- skill gems
Skill gem (known as Active Skill Gems in item filter), is an item class which grants active skills to the player by placing them into an item socket. Similar to support gems, skill gems can gain experience and level up increasing both their Attribute(s) and character level requirement as well as the effect of the stats granted by the skill.
Skill gems have gem tags which are used to categorize them, but note that gem tags are not intended to indicate whether a skill gem can be supported by other gems or whether specific stats (or modifiers) apply.
When it comes to mods or passive skills, such as Unnatural Strength's +2 to Level of all Minion Skill Gems , "skill gems" refers to [active] skill gems only.