You’re trained with a particular type of ranged attack, giving you a bonus to your attack checks with it equal to your skill rank. Each ranged attack is a separate Ranged Combat skill with its own rank, and encompasses a single weapon or power, although an array may be considered one power, at the Gamemaster’s discretion.
So a hero might have Ranged Combat: Guns or Ranged Combat: Fire Control, but Ranged Combat: Powers is too broad. Ranged Combat: Throwing is an option and includes both thrown weapons and objects a character simply picks up and throws.
The bonus from a Ranged Combat skill applies only to attack checks with the particular attack, not to defenses. For a broader bonus to attack checks that is less than simply raising Dexterity rank.
D20Hero SRD Skills article- http://www.d20herosrd.com/4-skills