The simplest type of carbon trade involves an entity preparing a contract that describes and specifies the kind of activity they are undertaking to either reduce or offset emissions. The contract may or may not be independently verified, although doing so will increase buyer confidence and probably attract a higher price. This contractual commitment is then sold to another entity that wishes to make use of the specified amount of the reduction or offset. Contractual commitments are usually traded "over the counter" (OTC), which means that the trade is usually a bilateral one between a willing buyer and a willing seller without the need for a market to exist. OTC trades are usually single trades where the terms are either partially or fully confidential. OTC markets are relatively simple and operate where there is limited "liquidity" (that is, not many trades are occurring) or where the product being traded is somewhat unique for each trade.
Whenever we drive or ride in a car, we are adding greenhouse gases to the atmosphere. And, when factories make the things that we buy and use everyday, they too are sending greenhouse gases into the air.