A preposition is a word that shows the relation of the Noun or pronoun it governs to some other words in the sentence; these are word used in a sentence (especially before a noun or pronoun) to show place, position, time, manner, cause,method etc. Prepositions cannot be inflated and they function primarily as headword in the prepositional group. Examples of prepositions are: at,on,in,to, for,by,across, under, over, until, since, within, through,etc.

The cloth is on the table
  Here, the preposition on shows the position of the noun 'clothe' in relation to the noun 'table'.

Let us consider the following examples:

He kept the book on the table (place)
The ball rolled across the road (direction)
She walked with her heels off the ground (manner)
The match begins at 4 p.m. (time)
The book is on the table (location/position)
I will attend the birthday party because of you (reason)
He ate the food without meat (manner)
I received the gift after the ceremony (time)

@Henkjan de Krijger #preposition

What is a preposition