Targeted: Melee attacks target individuals. A melee attack against multiple enemies consists of separate attacks, each with its own attack roll and damage roll. Melee attacks don’t create areas of effect.
Range: A melee attack’s range usually equals your melee reach. (Sometimes a power specifies that it affects only adjacent targets, though, so even if you’re using a reach weapon, you can’t attack more distant targets with that power.)
Reach: Most characters have a reach of 1 square. Certain powers, feats, and weapons can increase your reach.
Published in Player's Handbook, page(s) 270.