The PERFORMANCE SCHEMA was first introduced in MySQL 5.5, and provided some instrumentation.

With MySQL 5.6, the existing instrumentation has been improved a lot, and a lot of new instrumentation was added also.

Now is a good time to review the overall picture ...

The performance schema tables
In 5.5, the tables available are:

mysql> show tables;
+----------------------------------------------+
| Tables_in_performance_schema                 |
+----------------------------------------------+
| cond_instances                               |
| events_waits_current                         |
| events_waits_history                         |
| events_waits_history_long                    |
| events_waits_summary_by_instance             |
| events_waits_summary_by_thread_by_event_name |
| events_waits_summary_global_by_event_name    |
| file_instances                               |
| …