Card Types

There are four distinct types of cards:

Entity
The Entity card is a 'permanent' card - called this as it stays occupying soul slots after being initially cast. They are slow-play cards.

Host
The Host card is also a 'permanent' card. They are quick-play cards. When a host is cast, you complete the effect of the host and leave it on the field until it is to be discarded (as noted on the card itself).

Sacrifice
The Sacrifice card is a 'non-permanent' card. They are discarded to the graveyard as soon as the card effect has taken place. They are quick-play cards.

Global
The Global card is a 'permanent' card. They are cast from your hand for no cost, but only one may be on your side of the field at any point in time. Playing one when one is already on the field will cause the first Global card to be sent to the graveyard, with the second one then taking it's place. They are slow-play cards.