Attack

Attacking is the act of initiating a fight against a monster or - in case of PvP - another player to whom you declared hostility. It is either Melee or Ranged. The narrower meaning of the word only means physical attacks, not using spells and/or special abilities of a character against a monster or player.

"Attack" is the universal label of the skill in Diablo 2, while in Diablo 3 it more specifically alternates between 3 skill names:
 * 1) Punch (no weapon)
 * 2) Melee Attack (sword, etc)
 * 3) Ranged Attack (bows, etc)

Characters generally lose access to this skill at 2nd level (which they will attain by the time they kill the Wretched Queen) since then it is replaced by a secondary skill which can't be toggled off.

A demon hunter for example is forced to have Impale there which expends hatred (which they can't use if they're out of Hatred) while the left key is Hungering Arrow which is used to build hatred... but only if a bow is equipped.

Normal bow shots are essentially impossible at this point for them, they MUST be hungering arrows which pierces enemies and seeks more, making it hard to do targeted kills when trying to minimize XP gain.