This is the covering fire feat:
You can use the aid another action with a ranged attack against an opponent, regardless of whether the opponent threatens an ally. Range penalties apply to this attack roll. Choose one ally when making the attack.
If the attack is successful, that ally gains a +2 bonus to AC against that opponent's next attack, as long as the attack comes before the beginning of your next turn. All allies with this feat also gain this bonus against that opponent.
Are you attacking the opponent's AC or AC 10? If the opponent's AC, does it deal damage when you connect?
Aid another in combat is always against AC 10. Aid another does not do damage.
No damage, against AC 10 but includes penalties for range.
Basically you're firing a shot at the enemy to harass them to make it more difficult for them to successfully attack your ally.
It is just like the usual aid another action in combat, but the feat lets you do it at range, which is not usually permissible.