What does job syspolicy_purge_history do?

1.This is came with a default installation of SQL Server 2008.What does it do?

--It removes the policy evaluation history.When you create policies and evaluate them from time to time, the history is stored. the job removes the history of those evaluations based on a retention period. 

2.Can I remove this job?

--I would leave it there, it is there for a purpose in case you ever use policies, which is an integral part of sql 2008, it does no harm and has no impact.