A linter is a tool used in programming to analyze code for potential errors, stylistic issues, and programming best practices. It helps developers maintain code quality by identifying problems before the code is executed. Linters can be integrated into development environments, making it easier to catch mistakes early in the coding process. Linters support various programming languages, including JavaScript, Python, and C++. They provide feedback on issues like syntax errors, unused variables, and inconsistent formatting. By using a linter, developers can improve code readability and reduce the likelihood of bugs, ultimately leading to more efficient software development.