ESLint is a popular open-source tool used in software development to analyze and identify problems in JavaScript code. It helps developers maintain code quality by enforcing coding standards and detecting potential errors before the code is run. By using customizable rules, teams can ensure consistency across their projects. Developed by Nicholas C. Zakas in 2013, ESLint allows developers to create their own rules or use predefined ones. It integrates easily with various code editors and build systems, making it a valuable asset for both individual developers and large teams working on JavaScript applications.