Emacs is a highly customizable text editor that is popular among programmers and writers. Originally developed in the 1970s, it allows users to create and edit text files efficiently. Its extensible nature means that users can modify its features and functionality through a built-in programming language called Emacs Lisp. One of the key features of Emacs is its support for various programming languages and file formats, making it versatile for different tasks. It also includes tools for version control, email, and even web browsing, allowing users to perform multiple tasks within a single interface.