English is a complicated language.  It's rather annoyingly difficult in many respects, and somewhat simplified in others.  Many people have difficulty with English spelling.  The grammar has it's ups and downs, but here is some help.  This series is for those who would like to brush up on or learn about grammar and grammar terminology.

One of the simple things about English grammar is the Prepositions.  Unfortunately, it is also very difficult as well.  There are only a limited number of prepositions.  Once one understand the basic meaning behind them, they can seem rather simple.  However, there are two things that make them difficult.  One is when the are used together with verbs to make verb phrases.  The other is in idioms which is more difficult.

English doesn't have an extensive case system, instead we use separate words call Prepositions.  There are only a so many prepositions and phrasal prepositions and it is very hard to introduce new ones.

Prepositions introduce us to location (under, on, in) direction (into, towards, to) time (after, during, before) amongst other conceptual things (among/st, like, about).  Those are the literal meanings to these words.

However, we have a nasty habit when using them with phrases.  That is, we use them for a lot of idioms.  Phrases like, "Over your head," "In your heart," "on your mind," "on TV."  There are lots of phrases like this.

The last things are the verb phrases.  However, many linguists, like myself, don't really consider the 'prepositions' in these to be 'prepositions' at all.  We call them verbal particles.  These include such things as "make up," (which has many many meanings) "write down," "look up," "go out," amongst many others.  These are deadly because one doesn't know when they mean the literal meaning and when they don't.

There are several lists of prepositions online, I would recommend looking them up if you wish to find out more.