Mysql is an open source relational database management system (RDBMS) that allows for multi-threading and multi-user access. It uses SQL statements to manipulate and retrieve data, including data definition language statements like CREATE, ALTER, and DROP and data manipulation statements like SELECT, INSERT, UPDATE, and DELETE. The SELECT statement is used to query data from one or more database tables, allowing users to filter rows using a WHERE clause, sort results with ORDER BY, and group rows using GROUP BY.