Per BOL you get the following information:
Errors with a severity of >= 20.
Memory related errors (Errors 17803, 701, 802, 8645, 8651, 8657 and 8902).
Non-yielding scheduler problems (Error 17883).
Sessions that have waited on locks for > 30 seconds.
Sessions waiting for a long time on preemptive waits (waits on external API calls).
Read on to learn more of the things this session contains as well as a couple ways you can access the data.