Essentially, the Kyoto Protocol seeks to control a basket of six greenhouse gases in order to manage climate change effects. This basket uses the global warming potential (GWP) of carbon dioxide as a base unit, and measures the relative warming effects of other gases. The Kyoto Protocol entered into force in February 2005. 
To date, 165 countries have ratified it. These consist of Annex 1 Countries, which can be defined as most of the developed world (ex US and Kazakhstan) and Non Annex 1 Countries (developing countries). Annex 1 Countries collective emission reduction commitment is to 5% less than their level of emissions in 1990. Non Annex 1 Countries are those that are participating in the treaty though as yet do not have any emission reductions commitments. Non Annex 1 countries typically participate through providing Clean Development Mechanism projects i.e. projects that reduce present and future CO2e (CO2e is carbon dioxide and equivalent harmful gases) in the atmosphere.
