There are a lot of word classes in the Korean language such as nouns, pronouns, particles, numbers, counters, adjectives, verbs, etc. This chapter would be about nouns and how they are formed.

I'm already assuming you know the difference between a prefix and a suffix so I'll just go on ahead.

There are nouns that are derived/formed with prefixes. For example,

with the Native Korean prefix 맏 which means "first"
맏아들 which is actually 맏 (first) + 아들(son) so it will mean "first son"
맏딸 "first daughter"

the prefix 신 on the other hand is a Sino-Korean prefix meaning "new"
신인 means "newcomer" from the combination of 신"new" and 인 "person"
신학기 (new semester) = 신(new) +  학기(semester)

There are also derivational suffixes such as
꾼, a Native Korean suffix which means "doer" or "a person who..."
장사꾼(businessman) = 장사(business) + 꾼(doer) 
일꾼(worker) = 일(job) + 꾼(doer) 

another is 학, a Sino-Korean suffix which means "study"
수학 (mathematics) = 수(numbers) + 학(study of)
한국학(Korean studies) = 한국(Korea) + 학(study of)

In English, there is another word-class called, "Gerund" where nouns are derived from verbs by adding ~ing at the end of the verb. In Korean language, nouns can be derived from both verbs and adjectives by adding the suffix 이/기 at the end of the verb/adjective.

verb + 이/기 (the act of)
벌이 (income) = 벌(earn) + 이(the act of)
먹기 (eating) = 먹(eat) + 기(the act of)

adjective + 이/기 (quality)
크기 (size) = 크(big) + 기(quality)
길기 (length) = 길(long) + 기(quality)

So I showed you those because it is a useful way to develop another word carrying an additional meaning. You can familiarize yourself with other prefixes and suffixes to be able to expand your knowledge on constructing words.

Another way is combining morphemes. A morpheme is a unit that contains a meaning, that can be combined together with another morpheme/s to create another word.

Nouns can be single or multiple morphemes(single morphemes combined together).

Examples of single morphemes are:

나무 (tree)
산 (mountain)
물 (water)

First, there are the Native Korean words. These compose a