BaseX is a lightweight XML database that stores, queries, and manipulates XML data using XQuery and XPath. It offers multiple interfaces including a GUI, command-line tool, and HTTP REST API. The tutorial covers installation requirements (Java 17+), basic database operations (creating, opening, dropping databases), resource management (adding, deleting XML files), querying with XQuery, and HTTP server setup with authentication. The REST API enables programmatic access to databases and resources, supporting CRUD operations through standard HTTP methods.