Electron is a framework that allows developers to build desktop applications using JavaScript, HTML, and CSS. It allows building cross-platform apps that can run on Mac, Windows, and Linux. Electron apps can use native menus, notifications, and dialogs while also supporting common web technologies. Some popular apps built with Electron include Slack, Visual Studio Code, and Atom. Electron works by using the Chromium rendering engine and Node.js to run a web page and its JavaScript in a separate process.