Active skills in Path of Exile are contained in Skill Gems. While this adds a bit of clutter to the inventory this allows players more flexibility in customizing their characters, since they need to be equipped on your Path of Exile items. This guide will go over some gem basics that are important to know.
Improving the skill gems in your Path of Exile items
Each gem has its own level and experience. The strength and effects of the skill scale with the gem level. Gems equipped in matching-color sockets automatically gain experience alongside the character. Additionally, they gain a 10% bonus. Note that gems will get experience regardless if players get any. Just make sure the Path of Exile items you have gems on are equipped or are in the active weapon slot.
Before you level up the skill gems in your Path of Exile items
When a gem gains enough experience, it can then be leveled up. A player can do this by clicking on the level-up icon on the right of the screen. Note that gems, like most Path of Exile items, have requirements. This goes up with its level. If the character cannot meet the requirements, then the gem cannot be leveled up (the icon will be gray.)