Atom
Atom is a free, open-source, and highly customizable text and source code editor developed by GitHub. It is built on the Electron framework, allowing it to run cross-platform on Windows, macOS, and Linux. Atom is known for its hackability, with a built-in package manager and support for thousands of community-created themes and packages to extend functionality.
Developers should learn Atom when they need a lightweight, modern editor that is highly extensible and supports a wide range of programming languages through packages. It is particularly useful for web development, scripting, and collaborative coding via Teletype, and is ideal for those who prefer a customizable interface without the overhead of a full IDE. However, it has been deprecated in favor of Visual Studio Code, so it is now primarily relevant for maintaining legacy projects or learning about editor extensibility.