Prepositions are words or phrases that give information about where, when or how something takes place. They can be split into different groups.
1) Prepositions of time, such as at, during, before, after.
I washed my hands before lunch.
He went to sleep during the film.
2) Prepositions of position, such as on, by, in front of, behind, next to.
The cat sat underneath the table.
The picture hung on the wall.
3) Preposition of direction, such as towards, away from, over, under, around.
The bird flew over the rooftops.
The car accelerated towards the onlookers.
There are other types as well, giving information about how something is done, or who it is done with.
We went by car.
I went with my brother.