Prepositions are words that indicate location, direction, time, or other relationships between nouns. There are simple one-word prepositions like "in" and "on" as well as compound prepositions with multiple words like "instead of". Prepositions can be categorized as prepositions of place, which show where something happens; prepositions of time, which show when something happens; or prepositions of direction, which show where something is going. Examples are provided for each category of preposition.