There are 6 types of gems: PATK, PDEF, MATK, MDEF, HP, and Speed, and they correspond to these 6 stats.
1. Socket gems: you may socket gems on gears to increase their stats.
2. The number of sockets on each gear is determined by the gear’s level. As many as 4 sockets may be available.
3. You cannot socket more than one gem of a particular type on a gear.
4. Craft gems: you may use 3 gems of the same grade to craft one gem of a higher grade.
5. You can acquire gems from the Gem Shop or Cloudwinder.
(Socket gems panel)
(Craft gem panel)