The document defines prepositions and categorizes them into three types: place, time, and movement. Prepositions of place indicate the location (e.g., 'above', 'under'), prepositions of time indicate temporal relationships (e.g., 'at', 'during'), and prepositions of movement indicate direction (e.g., 'to', 'into'). Examples for each category are provided to illustrate their use in sentences.