I learned about prepositions in grade school language arts classes. Your teachers may have taught you how to use prepositions without actually teaching you the name.
Prepositions are a part of speech that many people do not pay attention to until they are in college. That being said, I learned about them in middle school.
prepositions are the words which gives a clear information about a thing like behind, in-front-of, near, beside, under, above, etc... this gives correct positions.