How do the skill gems and sockets work?

Edit2: I missed the huge section on skills on the site, which answers all of my questions, this thread may be buried now...

Edit: It seems I picked the wrong board. Could a kind mod please move this topic to the general section? Thanks.

Being a bit confused by the gem system, I decided to do a writeup of what I know and maybe edit to this post any answers found in this thread.

From various posts, streams and videos I was able to figure out the following:


Gems:

- Gems drop randomly all over the world.

- There are three colors of gems, corresponding to the colors of the stats:
* Red gems for stregth based skills
* Blue gems for intelligence based skills
* Green gems for dexterity based skills

- Any class can use any gem.

- The gems must be socketed into sockets of the appropriate color to grant the skill.

- Gems have XP and a level. I assume they level up as you use the skill? Are there any other ways to upgrade them?

- Skills aquired through gems can be enhanced by putting points in the passive skill tree.

- My guess is you can only have a maximum of five different gems in your gear, as there are only five skill slots (Hotkeys q to t).

- Depending on the socket used, gems can have two roles:
* Skill gems, which grant you the skill.
* Support gems, which augment another skill. Details are below, under "linked sockets".


Regular Sockets:

- Any item can have any color of sockets. For example there are bows with red sockets, or wands with green sockets. This allows unorthodox builds.

- Sockets can be rerolled independently from an items stats, allowing to improve an item with good stats but poor sockets further.


Linked Sockets:

- Linked sockets are found later in the game.

- The first gem you put into an item with linked sockets will give you the skill as usual.

- The gems after that augment the skill from the first socket, depending on what the skill is and which gem is used to support it.