4th Edition has unified the mechanics behind classes. No matter what class you pick you'll be using the same mechanics during combat. They're called attack powers, and there are three types of attack powers.
- At-Will Attack Powers
- Encounter Attack Powers
- Daily Attack Powers
Each character knows two at-will attack powers for existing, and each character knows at least two more for being part of a class. Humans know an extra at-will power from their class, and psionic classes are... different. Non-psionic classes also learn encounter powers and daily powers as they level up. You start with one encounter power and one daily power at level one, and you end up with three of each later on.
The two at-will powers everyone knows represent basic combat with hand-to-hand weapons and ranged weapons, and they are called "Melee Basic Attack" and "Ranged Basic Attack." Most of the time you won't use these, because your class at-wills are better.
Your class at-will powers represent a fighter's superior hand-to-hand skill, a rogue's dexterity and tricky ways, a cleric's divine blessings, or a wizard's magical power. You can use them all day long, as many times as you need or want to.
Your class encounter powers represent bursts of extra effort you can do. It might be a sword trick that only works when the enemy doesn't expect it, a spell that requires more effort than you can always use, or a divine intervention that only works so often. Once you use an encounter power, you can't use that same encounter power again until you take a "short rest" (5 minutes).
Your class daily powers represent the reserves of energy you can use when your life is in danger. These are the sword techniques that you can never get right during practice, the magic spells that are normally too complex for you, and the big life saving actions of gods. 4E assumes you're a big damn hero, and when the chips are down you
can pull off the dangerous forbidden technique. You can use daily powers whenever you want, but you can't use the same daily power again until you take an "extended rest" (6 hours).
How does this affect character creation? You pick two at-will powers, one encounter power, and one daily power. Then you try them out. If you aren't happy with them? You can switch them. (The published rules for "retraining" powers suck so we'll play fast and loose until you're happy with the powers you have.)