Prepositions are words that indicate the position of an object, such as "next to" in the sentence "Alice is sitting next to you." The presentation introduces some common French prepositions like "sur" (on/above/over), "sous" (below), "entre" (between), "devant" (in front of), "à gauche" (left to), "à droite" (right to), and their English translations. Examples of French prepositions are provided in a table for reference.