Small, fast database for simple tasks like providing services to web servers.

http://www.mysql.com/doc/en/index.html - manual

mysql --host=host --user=user -p database

(as root, connected to mysql database) select host, user, password from user;

show databases;
show tables;
describe table;

MAC

/Library/StartupItems/MySQLCOM/MySQLCOM

Installs into /usr/local/mysql by default.