Prepositions are very important to the meaning of a sentence. A misused preposition can make a clearly stated sentence a confusing jumble of words. They are difficult to learn because of the sheer number of them in the English language and their capacity to have many meanings.
There are different types of prepositions. Time prepositions include before, after, during and until. Place prepositions include inside, on top and between. And direction prepositions include across, up and down.