What are Magic The Gathering creatures?

Answer 1

A creature is a permanent that can (usually, but not always) attack or defend against attacks from other creatures. Underneath the picture there will be a short description of what exactly that card is, and it should say whether its a creature or not.

You can also usually identify a creature card by looking at the lower right corner. Two numbers separated by a slash (such as: 6/6 or 12/7) will indicate a creature.

Answer 2

A creature token is an object places on the field by a spell or ability, that functions as if it were a regular creature card. The token's colour and type will be set by the card that created it. Normally a creature token will have a converted mana cost of zero, but that's not always the case. A token that is a 'copy' of another creature, will copy the converted mana cost too.

As an example then, take Wurmcoil Engine. When it goes to the graveyard from play, you place two 3/3 artifact wurm creature tokens into play, one has Deathtouch and one has Lifelink. So to all intents, you now have two 3/3 creatures with the above attributes, and can do whatever with them that you'd do with regular creatures.

There's one other ruling regarding a creature token. They cannot exist in any other zone apart from in play, so if they are removed from play or destroyed, they go to the graveyard or removed from play pile (this can trigger cards that look for creatures being sent to the graveyard, for example) and then cease to exist, you do not keep the token card or whatever you used to represent them in the graveyard.