Preload? How to use them?

Preload? How to use them?

I saw at WE such commands as:
game - file preloading
game - Begin preloading with a 0.50 second timeout
game - Preload all files listed in filename


For what do they need and How may i use them ?

and What is it?

Preloading sometimes prevents lags with eyecandy models. For example, FlameStrikeTarget. It's very nicelooking but causes a first time lag. Preloading prevents this.