Term: Ability Range

The target of a Ability must be within the Ability's chosen range.

Most spells have ranges expressed in feet (unfortunately), and most commonly have ranges in increments of 5ft, in sets of 15 (15 ft, 30 ft, 60 ft, 120 ft, etc).

If a a spell has 0 ft of range, it considered a range of Touch⚙️ or Melee; which is different from a range of Self, which it technically targetless and a target in itself. Basically, you can target yourself with a Mage's Armor, just as you technically can with a point blank Faultless Fusillade, even though you shouldn't in the latter case.