Prepositions describe the relationship between words in a sentence. They usually come before a noun or pronoun and show their relationship through a time, place, or direction.
Examples of prepositions:
The dog lays beside the sofa. ⇒ Beside is a preposition of place.
After a few weeks, the flower began to bloom. ⇒ After is a preposition of time.
The woman slowly walked away from the mad dog. ⇒ Away from is a preposition of direction.