Here's how I understand it. The idealized version is that a polluting business that cannot clean up its act pays money as an incentive to a second business that can, but chooses not to because it hurts the bottom line and its own profitability. The carbon payment becomes a penalty financially lowering the profitability of the first polluting business but increases the bottom line of the second business that would be less profitable, or not exist at all without that credit payment. Because of the ongoing cost of carbon credits, the next generating plant built by business one no doubt will include cleaner emissions to eliminate the cost of the credits. This whole carbon credit trade speeds the transition time until business one puts up the new cleaner plant and by making polluting more expensive to the bottom line, speeds it along. Theoretically.
Local example: Florida Power and Light has coal and oil fired electricity generating plants built 50 yrs ago that cannot be upgraded to clean its smoke stacks without building an entirely new facility. It is just not cost effective and the existing plant may yet have another 20-30 yr life expectancy. So instead of building a new plant that is cleaner it might be cheaper do something to offset that polluting coal plant. It chooses the cheaper option. It could buy carbon credits from possibly a wind tower company that produces clean electricity so then the wind farm company becomes a profitable reality or it could just come to my back yard and build the wind tower farm itself, which it did. It produces the same result. The average kilowat of electricity produced by FPL just got cleaner when the coal plant and wind farms are averaged together. Who forced them to put up an offsetting wind farm or buy carbon credits? No one. They did it themselves but probably would not have been done either if there had been no future fears put in their mind that they might be forced to reduce their carbon emissions at some point by the EPA. They realize that the EPA regulation of carbon emissions is something that this way comes. The name of their clean energy investments is FPL Next Gen and includes wind, solar, geothermal and whatever other clean energy they can produce, or cause others to produce through carbon credits, to lower their average emission per KW. Anyway this is a simplified version of what actually happened here.
The Jackson Hole Airport may try this but unless it is done on larger scale by many airports, it will have minimal effect on the environment as a whole. The big gains will be made by the largest polluters and that is energy producers themselves. Jackson Hole airport might be tipping their hat to carbon neutral but their hat size is too small to matter and it comes off more like a parade of.. Look at Me, My Humility is Bigger Than Yours.