In Path of Exile, Active Skill Gems grant you abilities to make use of in game, but Support Skill Gems can enhance those abilities and produce them stronger. Getting Support Skill Gems is not hard, much the same way you get Active Skill Gems: by completing quests and looting from monsters. But connecting those Support Skill Gems to compatible Active Skill Gems is a lot more complex.

What do Support Skill Gems do?
Support Skill Gems can drastically customize the way your abilities work. If your Active Skill Gem is always to shoot one particular fireball, a Support Skill Gem could multiply the effect making it five fireballs. Another POE Trade Support Skill Gem will make the same fireball result in a bleeding effect, or increase its burn duration.
With Support Skill Gems, you'll be able to turn nearly every basic ability into a remarkably powerful attack. When you want to get POE Currency and POE Items, I think you should visit MMOAH. Their POE trade is safe and cheap. Buy cheapest POE Currency from MMOAH!

How will you link Support Skill Gems with Active Skill Gems?
A Support Skill Gem does nothing and not using a connection to an Active Skill Gem. If you slot a Support Skill Gem to a socket by itself — without the need of connections — it can level up periodically, but offer no benefits. Support Skill Gems be important when you have two connected sockets, which seems like a gold line between some sockets, as found in the image above.
If you placed an Active Skill Gem into on the list of connected sockets, you are able to augment it with many Support Skill Gems — depending on how many slots the armor piece or weapon has. As long as you’ve correctly linked two abilities, the Support Skill Gem will increase the Active Skill Gem.
You must place a Support Skill Gem within a socket which fits its color – similar to Active Skill Gems. If you want to make the ultimate combo between Support and Active Skill Gems, you'll need a group of perfectly rolled sockets on your own gear piece.
Some Support Skill Gems really have restrictions. A bleed Support Skill Gem will not be able to affect a minion summoning Active Skill Gem, by way of example. To avoid setting up a poorly linked spell similar to this, you'll want to read the tooltip for each Support Skill Gem before you determine it. It will always notify you what forms of abilities it wouldn't support.

Two Active Skill Gems cannot support 1 another, regardless of whether connected. If you have an association socket, attempt to only POE Currency place one Active Skill Gem within the group, and utilize the other connecting slots just for Support Skill Gems.
Most Active Skill Gems are powerful by themselves, but if you are able to master linking them combined with Support Skill Gems, you'll unlock to be able to devastate a place full of enemies.