Attacks may be declared against players, or Planeswalkers. Attacks may not be declared against other creatures.
Some creatures or cards have "do x to deal x damage" (i.e. tap to deal one damage to target creature or player). This is different from attacking and you should not confuse the two.
With creatures, you can only attack a player in the combat phase. The main goal of the game is to reduce the opposing player(s) life total(s) to zero. Or, to give them 10 poison counters.
No, unless they have haste.
Creatures with Flying may block creatures that don't. Note that in Magic, creatures do not 'attack directly' as such, they are declared as attackers, and then creatures may be declared to block them. The creature with Flying in this case, can block creatures with, and without Flying.
Whenever a creature with lifelink deals damage, (combat or otherwise) to a creature or player, you gain that much life.
The ability "Defender" is actually a disability, a creature with defender cannot attack. Creatures with Defender often have "Wall" as their type.
An Ooze token is a creature that can be created. The token card is the representation of that creature.
Vigilance just means the creature does not tap when it attacks. It can be tapped by other spell or abilities, or as the cost for an ability that requires tapping - and must of course be untapped for it to be able to even declare an attack.
A giant deck is a deck consisting of the creature type giant.
'Casting a creature spell' means to pay the mana cost and put the creature spell on the stack. If this is allowed to resolve, then the creature enters the Battlefield.
Creature: rat ninja Mana cost:4B Abilities:Ninjutsu 2B, Whenever Throat Slitter deals combat damage to a player destroy target nonblack creature that player controls Power:2 Toughness:2
Creatures are not brought into play tapped, but they have summoning sickness preventing them from tapping to attack or to tap to activate any abilities unless they have the keyword "haste".
Single cards that represent a creature (token) there are currently 199 that I am aware of.
If creature has Reach, it can block flying creatures without having to have flying itself.