Original Post — Direct link

I've seen a ton of articles and videos on youtube naming Skill Variants as Skill Mods and quite frankly this is going to become a problem unless addressed so, here it goes.

Skill Variants Purchased with SHD Tech to add a varient to a Skill. Example : (Hive - Reviver Variant) (Shield - Deflector Variant)

Skill Mods Obtained as a loot item or crafted and can be slotted into a Skill item to provide attribute bonuses. Example : (Turret - +15% Deploy time) (Firefly - Targets a additional enemy)

Know the difference.

External link →
about 5 years ago - /u/TotalyMoo - Direct link

You can always check this infographic for all the details :)

http://static2.ubi.com/pxm/TCTD/AG/TD2/Assets/Infographic/Character_Progression_Division2.jpg