What is that last bit about not being an attack action or a free attack action mean? Is that whats allowing the unit to attack two different targets? I thought it meant he basically attacked twice against two different targets in an activation. but can a unit with gunslinger not move ---> Ranged attack Target 1 | Ranged Attack Target 2?

Units are limited to one” attack action” per activation. That line is just emphasizing that the additional attack from gunslinger is an “attack”, not an “attack action”, and is therefore not limited by the once-per-activation rule.

Also, some abilities may trigger off of an attack action, but not an attack. Those abilities wouldn’t trigger off of Gunslinger (as an example look at Relentless: it triggers off of move actions, not moves).