Pragmatics is the study of how language is used in everyday interaction. It's part of linguistics, which is the scientific study of language.
Pragmatics is the branch of linguistics that analyzes how people really use language. It goes beyond just looking at words — pragmatics is about how words are used in different situations. If you're a linguist studying pragmatics, you're going to need to hear real conversations between people. How people think they use language and how they actually use it aren't quite the same, and pragmatics is about looking at the reality of language use.