As you said, cap-and-share is a form of cap-and-trade. Once we agree that cap-and-trade is the way to go, the next question is how to allocate the emission allowances. This is a decision where efficiency and equity both play a role.

There are many ways to allocate allowances. Allocation decisions can weigh factors like the emitter’s relative contribution to the problem, the economic wherewithal of different sectors or firms, impacts on efficiency, and of course, equity.

Another way is to distribute allowances is through an auction, with the proceeds going to the government. Emitters would then purchase allowances in the auction. Auction revenues could then go to a variety of public purposes including transition assistance for workers or assistance to communities impacted by climate change.

The way that allowances will be allocated, by "sharing", by auction, by administrative determination, or by some combination of all of these – is one the issues that the Congress will have to wrestle with.

http://www.capandshare.org

I've made a quick clip explaining cap and share in 49 seconds:

http://www.youtube.com/watch?v=ZX9ky8SO8aM