Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
Q. How definition update work? It will pull by my SEP from the computer or it push from Symantec server?
--> It can be either way, it's a part of configuration either Push Mode or Pull mode.
Q. Any schedule push from Symantec server?
--> You can't schedule push from Symantec server. But many customer prefer to update client definitions during midnight time. In such scenerio we do suggest to configure SEPM liveupdate in the midnight itself and configure clients in Push mode. As a result as soon as SEPM receives definitions it starts distribution.