VOD Pull vs VOD Push
The major difference between VOD Pull and VOD Push is:
VOD Pull - The CDN will fetch the video files from the origin, the user specified and distributed to the streaming edge servers and delivered to the end users.
VOD Push - The CDN will fetch the video files from the Streaming Storage Server (which contains the user file uploaded in advance) and distribute it to the streaming edge servers and deliver to the end users. You will need to create the streaming storage server from your control panel and it would cost $50/month as wowza software would be installed on the streaming storage server.