Quote Originally Posted by Heenan
Focus Target
Create a focus for the thing I currently have targeted
(store target into memory)
Let's not confuse this with "focustarget", which is your focus' target.

Ie, /cast [target=focustarget] shadow bolt, which will cast a shadow bolt on my focus' target.

I think the simplest answer to the original question is that focus is basically a second target that is stored locally.

So, essentially, you have two targets you can assign independently. And then, in macros, you can append 'target' to the end of each of these to get that unit's target.. So you can have focustarget targettarget and targettargettarget, etc.