Hello guys, I am new to Triggering and SCII Mapping in general, I am looking for a way to make Camera X follow Unit Y, everywhere that Unit Y Moves.

Essentially, I want to make a Camera that is shot 'over the shoulder' of my Unit.

I believe the "Make camera follow unit group" trigger is what you are looking for. Just make your unit a unit group (Variable would work best) and use that trigger, then all you need to do is set of the different angles of the camera and you are set.

I don't completely understand Unit Groups yet, what triggers am I looking for in order to set a unit group, and what kind of conditions or events are typical for creating unit groups, adding units to unit groups or removing units from unit groups?

When you initialize the game, or create your "Hero" unit (Who will be your shooter which is what I am assuming you are making) simply add him to a global variable of type "Unit Group" using the "Add unit to unit group" trigger. Once that is done you can just use the "Follow unit group with camera" trigger to make that player's camera follow the unit group that has only one unit. This is the smoothest way to do it, you could just move the player's camera every game loop, but that makes it feel choppy and it doesn't seem right.

Conditions - Things that have to be true for the trigger/action to occur, in this case, you might want to make sure that it is the correct unit you are following (Like it is yours and not some other players) but other than that you probably wouldn't need any conditions

Events - Either map initialization (If you already have the unit you want to follow created), or when you create the hero unit is when you would want to add the unit to the "Unit Group" variable and then make the player's camera follow the unit group.

Hope I helped =/

http://www.galaxywiki.net/Starter_Guide
This should help.

Events define when a trigger is triggered.
Conditions are verified when Events are met. Conditions precise more conditions required for a trigger to be triggered. If Conditions are not met, the Actions will not be fired.
Actions contain everything that must be triggered when Events and Conditions are met.

Global Variables can be used everywhere and referenced everywhere. They are independent from triggers.
Local Variables are only used within the trigger they are called in. They are situated inside the trigger itself (in one of the sections like Events, Conditions and Actions inside the trigger). You can thus have multiple Local Variables of the same name in different triggers.

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This tutorial will help you out on your quest:
http://www.galaxywiki.net/Custom_Camera_Setting_%28First_Person_and_Third_Person%29

Thanks guys, I will definitely try and look in to this and give it a try. And for the record, yes, I am trying to create a shooter x