A Preposition is a word (or group of words) that links together the parts of a sentence. They can be used to situate things in time, in a location, in a direction, etc.
The cat is in the house.
I have been studying English since 2015.
In the first example, the preposition in places the cat in a particular location.
In the second example, the preposition since tells us how long the action has been taking place.
There are many different prepositions, and they can play a variety of different roles. Here are some common ones:
There are of course many more prepositions in English and as you keep learning you will slowly discover them.
Some Useful Tips:
Don't directly translate prepositions from your native language into English. This can often lead to a mistake.
Keep reading and listening to LingQ content to see the most common prepositions and what situations they are used in. The best way to learn is to keep reading and to try to note which prepositions native speakers tend to use.