esquery is an ECMAScript AST query library, enabling powerful selection and filtering of nodes within JavaScript code represented as an Abstract Syntax Tree (AST). Think of it as CSS selectors, but for JavaScript code structure. Developers use esquery to analyze, transform, or validate JavaScript code programmatically. It supports a wide range of selectors, offering precise control over AST traversal and node identification, simplifying tasks like static analysis, code modification and refactoring tools.