Controlled feed means that the bolt face is recessed at the bottom, allowing the cartridge head to slide under the extractor before the cartridge is released from the magazine. It just means that you can chamber a round with the rifle in any position without the cartridge falling out of the receiver. It works fine but isover rated. 98 Mausers are built this way, and of course some Win mod 70's & Ruger 77's

Push feed just means that the bolt pushes the round forward and up, out of the magazine without actually grasping the head. The extractor doesn't engage the cartridge head until the bolt is closed. So, if you're holding the rifle upside down while chambering a round, (when will you ever do that?) the cartrdge will fall out.Remington 700's are built this way.