Many ways, but for example related to prepositions of place: "On" means that: something is placed above something "the cat sat on the mat"; something attached to something "the clock was on the wall"; or for within buildings, i.e. "my office is on the third floor." "In" means inside something: "My card was in my wallet," "he lived in a different town," "meet me in St. Louis." "At" refers to a place where something specific is happening: "they were at the new restaurant until it was very late," "at the library you have to speak quietly." This is not an exhaustive explanation because this is a big area.