SQLAlchemy is a Python SQL toolkit and object relational mapper that provides a full-featured SQL expression language while also allowing direct SQL execution. It features a core component that handles engine, connection, dialect, metadata, table, and column objects to work with databases, along with an ORM that builds on the core to allow mapping classes to tables with relationships and querying. SQLAlchemy supports all major databases including PostgreSQL, MySQL, MSSQL, SQLite, Sybase, Drizzle, Firebird, and Oracle.