Slow-play vs Quick-play

What is the difference between card speeds?
Playable cards come in two main categories - slow-play cards and quick-play cards.

Entities and Globals are slow-play cards.

Host and Sacrifices are quick-play cards.

The only difference between these cards are when they can be played. Slow-play cards may only be played in your own main phase, while quick-play cards may be played whenever a new phase is entered (on your and your opponents turn) as well as during your own main phase, and also when responding to other cards and their effects.