The document defines and provides examples of different types of prepositions in English. It states that prepositions indicate the location or position of a noun and show the relationship between nouns, verbs, adverbs, etc. The document discusses simple prepositions like "on, under, off"; compound prepositions formed by combining a preposition and noun, adjective, or adverb like "among, behind"; participle prepositions formed from verb participles like "assuming, barring"; and phrase prepositions that behave as prepositions but are groups of words like "on behalf of, instead of". It also notes some words can be used as both prepositions and adverbs depending on whether they have an object or not.