Unlike most ARPGs, Path of Exile's profession does not specify which skills players can use. Every class can be used from the beginning, except for Scion, which must be rescued at the end of Act 3 to become a playable character. Each class starts with its own passive tree part. As implied, the passive tree itself is the same between each class, so its size is daunting.
Each class in Path of Exile has an advanced class that can be unlocked throughout the course of the campaign. These advanced professions, called Ascendancy, provide a unique passive tree, each of which grants build-enabled features. Every profession except Scion has three Ascendancy options that they can choose, and Scion has only one Ascendancy option. Players need to Buy Chaos Orbs while completing tasks.
Support Gems are gems that can be set and only provide buffs for Skill Gem. These gems support skills, they do not grant skills. Support Gems need to do two things to work: There must be a link connecting the Skill Gem and Support Gems slots on the gear, and the two gems must share at least one tag.
Tags are a simple concept that most new players ignore. For simplicity, Tags are attributes that the gem represents as text. You can find the Gem tag directly under the gem name. If skills and Support Gems share at least one tag, they are compatible with each other. The system itself is not too complicated. If the player cannot easily determine whether Support Gems are suitable for a particular skill, please remember Gem Tags. In addition, players buy POE Currency is also a good choice.