From StrategyWiki, the free strategy guide and walkthrough wiki

[edit] Attributes

In Ghost Recon, characters start 1 or 2 points in each of the attributes:

• Weapon: Improves recovery time (but doesn't increase accurracy.)
• Stealth: Reduces the distance at which enemies can detect you
• Endurance: Allows taking additional damage (note that you can still be killed in one hit).
• Leadership: Every three points in leadership boosts all attributes of teammates in the platoon by 1.

[edit] Specialists

Specialists are made available when you complete the optional objective in a mission. These soldiers appear with better training than regular soldiers, but if killed, are not replaced.