A collection of software designed for advanced MySQL/PerconaServer tasks, maintenance, and monitoring.
Percona Toolkit is a collection of advanced command-line tools created by Percona support staff for the purpose of setting up MySQL and system tasks that are too difficult or complex to perform manually.
See the official percona website for a more comprehensive description of the Toolkit.
It is a very enhanced upgrade from its Predecessor : MAATKIT (also created by Percona)