Socket links, what do they do?

I got an orb of fusing and it mentioned socket links. I see what they are visually and can recognize them now but what do they do?

u can link support gems 2 ur active gems

Some gems give you skills; you're familiar with those. Other gems do not provide skills by themselves but rather change skills by adding damage or increasing the duration of effects or increasing the number of projectiles or any of a number of modifiers. For these non-skill gems (called "support gems") to work with skill gems, the sockets they are mounted in must have a link between them.

In the case of more than two sockets being linked, you can do some pretty cool stuff. Let's say you have three sockets A, B and C and there are sockets between A-B and B-C. In this case, all the sockets are considered connected. You could put Added Lightning Damage in socket A and then put Cleave in socket B and Leap Slam in socket C. The result: Added Lightning Damage affects both Cleave and Leap Slam!!

Yah the possibilities with higher link counts are pretty neat.

Multiple linked sockets:

* Can chain multiple support gems to a single skill for crazy damage (and equally crazy mana cost as they have mana cost multipliers)

>> Common for main skills (i.e. Groundslam + faster attacks + melee physical damage + added fire damage + life leech)

* Can link single/multiple support gems to multiple skills to get maximum coverage

>> Common for support skills/auras/curses (i.e reduced mana cost + grace + anger)