Ok, first off, i don't really know what this is called so I couldn't really search (it tried, though)

So what i mean by this is.. say for example my marine is somewhere in the map. I bring a ling to a beacon then it teleports to marine(or somewhere near). The ling must always teleport to the marine, wherever it is. For example, in certain mass games, there is a unit dropper. It drops units you pick to the location the unit dropper is at.

Thanks in advance!

This is actually pretty simple. You are going to want to set up a trigger like this:

C:
Current player brings 1 ling to "teleport beacon"
Current player commands at least 1 marine

A:
Center location named "Location 20" on marine owned by current player at "Anywhere"
Move all lings at "teleport beacon" to "location 20"
(optional center view or display text)
Preserve trigger.

OK, in SC mapping we use 'locations' - virtual boxes you cannot see in game. You can detect units in those boxes, perform some actions on those units and move these boxes around, too. So what you need is to create one location around the beacon (call it "B") and one small location anywhere on the map (call it "M"). Then create the trigger:

CONDITIONS:
-a zergling is brought to location B

ACTIONS:
-move (center) location A to the marine
-move zergling at location B to location A
-preserve trigger (this action makes the trigger re-useable, so this trigger will work every time the condition is met, not just once)

NOTE: The language I used for the trigger is not how the actual conditions and actions will appear in the editor. I want you to figure them out for yourself. Also please check out the FAQ pinned topic in the Map Making Assistance forum.