Outfitter simply helps to quickly switch gear sets, in much the same way as the one that Blizz introduced, but Outfitter has more customisable features and frankly, works more smoothly in my opinion.
Clique is a nifty little addon that let's you bind things to your mouse buttons.
It works by having another tab in your spellbook (like the tab for balance spells etc) and when you click it, it opens up. Then you go through your spellbook assigning spells to different button+mouse combinations.
eg. My Wild Growth is set to shift+right click, Nourish is shift+left click etc.
Whenever you are over the players frame (the little picture of them) you can click with whichever button pressed and it will cast the spell that you set. You can also set macro's, though I haven't bothered yet.
It also works with many raid frame addons, which is why people suggest grid as you can click cast spells on the grid frames.
I personally use grid+clique and find it the best combo so far (even better than healbot (/flee))
I'm tired, so if that makes no sense I'll check it in the morning...
who am I kidding? I'll be checking out the new patch in the morning