Most services (like YouTube, Netflix, etc.) transfer data direct from their servers to your Chromecast, without your phone or laptop in the loop for anything more than a remote control. It means you can start Netflix running for the kids from your phone and then go out to run an errand and it will keep playing.

VLC could do that for network sources. Even for a local file source, it could copy the whole file over - the Chromecast has a decent amount of RAM.