Still people have not given you clear explanation. It is just simple.
Your company in your county is emitting carbon gases beyondd the allowed limit. Whereas my company near a village in India does not emit even to the allowable limit. This is bcos I have huge plantations, cultivations, forests and enourage aforestation. This will help to arrest the pollution through emission.
So my carbon poluution quota level is still more. ie., I can even pollute more here. This quota level can be purchased by you for money from me.
I will keep on increasing my carbon emission prevention methods and thereby save the credits to be sold to people like you.
Say my company has 50 acres of ecalyptus or teak or redwood trees, and continues to grow more every year. Then pollution is nil from my side. I have not used the pollutable quota now. So I am selling it to you based on the Carbon Credit Climate Exchange points similar to SENSEX.
You and I could grow trees on large scale and companies here can adopt our trees by paying money to us. Land is mine,tree is mine and I have to just maintain it without cutting. So your trees pay you.
Hope I have explained you clearly. For any other details on any topic also, please free to drop me a mail I love to explain always.