As the name suggests, it is used to gather data for the oracle performance manager, spacial index tools and etc. This is soly, used by the OEM. If you are planning to run any statistics related operation from the OEM on Windows, like oracle tuning pack, performance manager and etc, you would require to start the data gatherer on the server where your instance lives.

the way to start it is

vppcntl -start
vppcntl -status

to stop:
vppcntl -stop

Sam