Deixis refers to linguistic expressions that depend on context for their interpretation. There are three main types of deixis: person deixis refers to pronouns like I, you, he; spatial deixis refers to spatial relationships like here and there; and temporal deixis refers to temporal relationships like now and then. Deixis is important in linguistics because it shows how language relies on and reflects the context in which it is used. Grammatical structures like direct and indirect speech demonstrate the difference between proximal and distal deixis.