mtg card type definition Magic: the Gathering Basic Definitions: Part 1 MTG Part 4: Cards Types

Well, this hand isnt great, but it has a couple of mana sources, a piece of removal, as well as two huge bombs that can create a ton of card advantage if we can stay alive long enough to use them

The difference between the two is what cards are banned and what cards are restricted

That ability is "when the last defense counter is removed from this permanent, exile it, then you may cast it transformed without paying its mana cost." This means that if for any reason a battle enters the battlefield without defense counters, it will be put into the graveyard and its controller will not get the chance to exile it

Being a hybrid card also makes it a more diverse combo piece