The freely accessible Wikipedia website provides a simple summary of key aspects of the Kyoto Protocol. Excerpts from this summary are included in edited form below.
Objective of the Kyoto Protocol
Kyoto is intended to cut global emissions of greenhouse gases. Or, for the more scientifically minded, the objective is the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system."
The agreement by those who ratify the Protocol
The Kyoto Protocol is an agreement made under the United Nations Framework Convention on Climate Change (UNFCCC). Countries that ratify this protocol commit to reduce their emissions of carbon dioxide and five other greenhouse gases, or engage in emissions trading if they maintain or increase emissions of these gases.
Now that Australia is ratifying the Kyoto Protocol this leaves the USA as the only developed country not to ratify the Protocol
The treaty was negotiated in Kyoto, Japan in December 1997 and came into force on February 16, 2005