J.L. Austin was a really smart man who was interested in how we talk and use language. He thought that the way we use words isn't just about the words themselves, but also about what we're trying to do with them.
For example, saying "I promise to do my homework" isn't just about the words "I," "promise," "to," "do," "my," and "homework." It's also about the fact that we're making a commitment to actually do our homework. Austin called this kind of speech act a "performative," because saying it actually does something - it performs an action.
Austin was interested in studying performative language and how it works. He wrote a lot of books and essays about it, and people still study his work today!