Types, Supertypes, and Subtypes
The card types are: artifact, creature, enchantment, instant, land, planeswalker, and sorcery. There’s also the weird ones: conspiracy, phenomenon, plane, scheme, tribal, and vanguard. Whenever you refer to one of these, you write it in lowercase.
Supertypes are a descriptor that can have rules meaning. The supertypes are basic, legendary, ongoing, snow, and world, and you refer to them lowercase as well. When you refer to them you don’t put an article in front: compare “becomes legendary” with “becomes a creature”.
Subtypes appear after a hyphen. They can’t have rules meaning, but cards can refer to them. That means you can invent a subtype for creatures called Flergs, and you can make a card that gives all Flergs +1/+1, but you can’t write a new rule to say that every deck must contain a Flerg. What an awful example. There are too many subtypes to list here, but all the creature types and artifact types are among them. Note also that each card type has its own linked list of subtypes, and they don’t cross over. An artifact can’t be a Soldier unless it’s also a creature. You always capitalise subtypes.
Permanents, Spells, and Objects
When a card wants to reference another object, it must use different terminology based on what it’s trying to affect.
A card references a creature when it wants to affect one currently on the battlefield. For example, Doom Blade.
A card references a creature spell when it wants to affect one on the stack. For example, Essence Scatter.
A card references a creature card when it wants to affect one in a graveyard, in exile, in a hand, or in a library. For example, Macabre Waltz.
This rule isn’t just true of creatures - whether you’re affecting instants, lands, or planeswalkers, this is the convention used. Therefore, since instants and sorceries are never on the battlefield, you will only ever refer to them as spells (if they’re on the stack) or cards (if they’re anywhere else).