I'm quite aware that there are multiple resources for Korean language learning, but I'm just posting this for the fact I got words mixed up and some phrases and words are used frequently that I never realized before. So, here ya go.

Basics:
언니 - what girls call older girls - means "like a sister"
누나 - what boys call older girls.
오빠 - what girls call older boys - meant to be "like a brother," but also used in the context of "boyfriend."
형 - what boys call older guys.

엄마 / 어머니 / 어머님 / 어머니님 - Mother. Informal, formal, what you call a friend's mom or a lady, and extra formal.
아빠 / 아버지 / 아버님 / 아버지님 - Father; same context as mother above.

아르바이트 - ah-leu-bah-ee-teu - part time job. Very common in Korea.

Descriptive Sounds:

반짝반짝 / 빤짝빤짝 (banjjak banjjak, bbanjjak bbanjjak) - Twinkle twinkle, to sparkle, to shine, etc. Girl's Day's Twinkle Twinkle is a good example of the word.
따끈따끈 (ddaggeun ddaggeun) - feeling warm or a feeling of warmth.
방글방글 (bang-geul bang-geul) - to smile brightly, to beam
빙글빙글 (bing-geul bing-geul) - Round and round, to spin ; U-KISS's Round and Round is a good example here.
보들보들 (bodeul bodeul) - Soft and cuddly.
뽀글뽀글 (bbo-geul bbo-geul) - boiling water
미끌매끌 (miggeul may-ggeul) - slipperly; from 미끄럽다 (mi-ggeu-ruhp-dah) to be slipperly
올긋볼긋 (ole-geut bol-geut) - to be many colors

쉿! (Shwit, Shht) - Shh, hush, shut up. [Literally is close to '']
두근두근 (dugeun dugeun, doo-geun doo-geun) - pitter patter of the heart; a lot of korean songs have this.
쿵쾅 (koong kwang, kung kwang) - heart beat, fast racing heart, heart throbbing | IOI's Crush is a good example.
쾅 (kwang) - Crashing sound
짝짝짝 (jjak jjak jjak) - clapping
똑똑똑 (ttok ttok ttok) - knocking.
쪽 (jjok) - kiss
뽀뽀 (bbo bbo) - kiss
음 (mm, eum, uhm) - Hmm, umm, mmm...
앗! (aht!) - ouch, ah!
냠 / 냠냠냠 (nyam, nyam nyam nyam) - eating, chewing, literally a cute way of chewing food
드르렁 (deu-reu-rung) - snoring
으르렁 (eu-reu-rung) - growling | EXO's Growl is a perfect example.
엉엉 (uhng uhng) - crying ,sobbing

딩동 (ding dong) - obviously a door bell
댕댕댕 (daeng daeng daeng) - clanging sound, or used when something is a wrong answer
빵빵 (bbang bbang) - car horn, apparently.
빵야 빵야 (bbang-ya bbang-ya) - shooting someone (w love or smth)

Animal Sounds:
찍찍 (jjik jjik) - mouse
꽥꽥 (kwaek kwaek, quack quack) - duck
멍멍 (muhng muhng) - barking
야옹 (ya-ong) - meowing
꼬끼오 (kko-kki-oh) - rooster crowing
구구 (koo koo) - pigeon coos
 

Exclamations / Expressions:

헐 (Heol / Huhl) - What?! What the... OMG
헉! (Huhk! Heok!) - OMG
대박 (Daebak) - Awesome, that's cool
아싸! (Assah) - Awesome, yay, yes!, hooray/hoorah!
우와 (Ooh-wah) - Wow
엄마야 어마야 (Eommaya, Ummaya) - OMG, use when surprised or shocked; The 어마야 is similar to mother, so it can be described as shouting for your ma when surprised.
어머나 (eo-meo-na, -uh-muh-na) - Oh my gosh; being shocked
감짝이야 (gamjjak-ee-ya, gamjjakiya) - That shocked me, OMG; being startled
아! (Ah!) - By the way/stopping someone, ouch
참 (cham) - By the way/stopping someone, also
어? (Eo? Uh?) - Huh? What? What is it? || Sometimes used as a reply 어 like saying 'yeah'
네 (neh) - Yes, yes? || Can be pronounced like 'deh' or formally with 'yeh'.
진짜 / 진짜로 (Jinjja / Jinjjaroh?) - Really? Seriously? || Can someties be rhetoric. Like if you're surprised by an announcement and you're like "oh wow really?" you don't need an answer.
정말? (jeongmal, jungmal) - Really? || Very similar to 진짜
그래 그래요 그래서 (geurae, geuraeyo, geuraeseo) - Really? Is that so? || The 'yo' makes it more formal. 'Geuraeseo' is more of a conjunction, but I've seen it used in terms of 'really then what?'
왜 (wae) - Why? What? Huh? What is it? || Although it truly translates to 'why' in most cases, it is used as 'what' in a lot of ways. Confusing, right?
아니야 (aniya) - A more informalized way of saying 'aniyo'; It literally means like 'that's not it' or 'no!' and being dramatic.
싫어 (shireo) - No, I don't want to, I don't like it
짱 / 짱이야 / 짱이다 (jjang, jjangiya, jjangida) - Awesome, That's awesome, It's the best, you're the best
아이고 / 아이구 (aigo, aigu) - Oh my gosh! Oh! Oops! | Basically a frustrated noise, too.
아이쉬 아이C (aishi) - ! OMG why, ,damn it
고고! (go go) - Being excited, going somewhere
콜 (kol) - Call! | Like agreeing to something.



 

Conjunctions:

그래서 (geuraeseo, geuraesuh) - From above, it is used in conjuctive context as 'so, so that, therefore.'
그리고 (geurigo) - and
그런데 (geureonde) - However, but, but then
그러면 (geureomyeon, geuruhmyun) - However, then, In this case, So then
그래도 (geuraedo) - And then, So that, Even if/Even then, However, Nonetheless
아니면 (animyeon, animyun) - Used as a link, but it's like saying 'or, if not, then' (ex. This happen, if not then, this happened; the connection is where animyeon would come in.)
때문에 (ttaemuneh, ddae-moon-eh) - Because of  (used a lot in cases of 'because of you 너때문에)
만약 (manyak) - If
하지만 (hajiman) - But || Not to be confused with 'hajima 하지마' which means 'don't go.'
그냥 (geunyang) - Just, but can be used as 'then, and so'
그렇지만 (geu-reoh-ji-man, geu-ruh-ji-man) - However, But then


 

Slang: (my faves okay.)

여친 남친 (yeochin, namchin) GF, BF. 여친 is also shortened for girl group GFriend's Korean name.
놈 (nom) - Man, person.
나쁜놈 (nappeun nom) - Literally means 'bad man,' but can be used as a bad insult to guys.
남사친 (nam-sa-chin) - Just a guy friend, not a BF
얼짱 (uhljjang, ulzzang) - Best face. Used on people online who have beautiful/handsome faces.
변태 (byuntae) - ert. Taeyeon's nickname is Byuntae.
몸짱 (momjjang) - Good looking body.
셀랩 (sellaeb) - Short for celebrity. Basically celeb.

ㅋㅋㅋ (keu keu keu) / 키키키 (kikiki, keke) - hilarious laughter
ㅎㅎㅎ (heu heu heu) & 하하하 (hahaha) - laughter
ㅍㅎㅎㅎ (peu heu heu heu) & 푸하하하 (pu hahaha)  - Basically puahahaha
헤헤헤 (hehehe)

셀카 (selca) - Self camera = selfie
비번 (bibon, bee-bon) - short for password 번호 (beonho)
뻥치지마 (bbeong-chi-ji-ma) - Stop lying!
노답 (no-dab) - Short for no answer (노 답답해)
노잼 (no-jaem) - Short for no jam/no fun, not funny. Used by BTS.
불금 (bool-geum) - Short for Fire Friday / TGIF 불 means fire and 금 is from the 금요일 which is Friday.

안물 (ahn-mool, anmul) - I didn't ask you; it's rude to say this.
멘붕 (men-bung, men-boong) - mental block
개소리 (gae-sori) - means 'dog sound' and to be used when you think a statement iswrong.
야매 (yamae) - fake/knock off
생축 (saeng-chuk) - short for 생일축하 or HBD Happy Birthday
알바 (alba) - short for 아르바이트 which is a part time job.


치맥 (chimaek) - Short for 치킨 chicken & 맥주 maekju beer
소맥 (somaek) - soju & beer
소콜 (sokol) - soju & cola
먹방 (muhk-bahng) - eating broadcast, popular online
일차 이차 삼차 (il-cha, ee-cha, samcha) - First, second, third round
맥날 (maek-nal) - short for McDonald's.
스벅 (seu-buhk) - Starbucks 스타벅스
 

Texting! (+ online chatting)

ㅎㅇ - short for 하이 which is 'hi'.

ㅇㄴ - 안녕
ㅋㅋ - laughing
ㅠㅠ / ㅜㅜ - crying
ㅎㅎ - laughing

ㄱ ㅅ - short for 감사 which is thanks
ㅊㅋ - short for 축하 / congrats
ㄱㄱ - go go

ㅈㅅ - short for 죄성합니다 / 죄성이요 which is sorry
ㄱㄷ - short for 기다려 which is wait

ㅂㅂ - bye bye

ㄷㄷ - 달달 shivering

ㄴㄴ - 노노 no no

ㅇㅋ - 오키 okay, but pronounced oh-key idk
ㅅㄱ- short for 수고해 / 수고 which is good job

ㅅㅅ - nice play (gaming)

ㅗㅗ - you

샘 - teacher / teach

방아 - nice to meet you

짐 - now

ㄷㅊ - short for 닥쳐 which is shut up. it's rude i think.

OTL ㅇㅜㄴ - is a guy on his knees, means disappointed
^^ - eye smile

^^; - nervous, sweating

>< - embarrassed

*^^* - blushing

@_@ - confused

-_- - serious

^3^ - kissing or kissy face

^_~ ^_< - winking

+_+ - surprised

Common words:

오늘 / 오늘도 (oneul) - Today
오늘 밤 (oneul bam) - tonight
밤 (bam) - Tonight, night time
시간이 / 시간 (shigan-ee, shigan) - hour
다시 (dasi, dashi) - again
자꾸 (jakku) - repeatedly, continuously, over and over
이제 / 이젠 (ije, ijen) - now, from now on (respectively)
영원히 (young-won-hee) - forever
항상 (hang-sang) - always
매일 (maeil) - tomorrow
내일 (naeil) - yesterday
날 (nal) - day
하루 (haru) - one day; when you say 하루하루 you are saying day after day.
평생 (pyung-saeng) - lifetime

심장 (shimjang) - heart
마음 (maeum) - heart, mind, head, chest, depending on context.
머리 (meori) - head, hair
가슴 (gaseum) - heart, chest
눈 (nun, noon) - eye
눈물이 (nunmuli, noon-mool-ee) - tears

하늘 (haneul) - sky | 하늘신 can mean God.
세상 (sesang) - world, can be used as an expression like 'omg'
바보 (babo) - fool, idiot

아름다워 (ahreumdawo) - you're beautiful
예쁜 / 이쁜 (yeppeun, ee-ppeun) - pretty
귀여워 / 귀엽다 (kwiyeowo, kwiyeobda) - cute, you're cute
잘생겼어 / 잘생기다 (jal-saeng-gyeosseo, jal-saeng-gi-da) - Handsome

슬픈 (seulpeun) - sad
행복 (haeng-bok) - happy
심심 (shim shim) - bored
피곤 (pigon) - tired
무서워 (museowo, moo-suh-wo) - scared
사랑해 (saranghae) - i love you
너무해 (neomu-hae) - i hate you, you're too much
좋아 (joha) - like, i like something
널 좋아 (neol joha) - I like you

떠나지마 (tteo-na-ji-ma) - Don't leave
하지마 (hajima) - Don't do it
가지마 (gajima) - Don't go

괜찮아 (gwaenchanha) - It's okay
미안해 / 미안 (mianhae, mian) - 미안 is less formal

네 / 예
아니 / 아니요

시원하다 (shiwonhada) - it's refreshing. siwo is refreshing. (/bricked)
마음이 아파 (maeum-i apa) - my heart hurts, my head hurts
보고싶어 (bogo shipeo, bogo shipuh) - i miss you; literally: i want to see you
anything w 싶어 means 'i want'

왔어 왔나 왔다 (wassuh, wat-na, wat-da) - You're here; Busan way of 'you're here'; you're here.
이거 (i-geo) - here's this
잘가 (jal-ga) - literally means 'go well'; say it when leaving someone.

 

Will be updated. <3