The radiocarbon dating method is used in order to determine the age of an object (fossil) by using the unstable radioactive Carbon isotopes. It is very widely used and is efficient for dating objects that are of very recent age.
The half life of Carbon-14 is approximately 5700 years. The half life is defined as the time required to decay half of its original composition. The carbon-14 is an unstable element and after it is completely decayed, it turns into Nitrogen-14, which is a stable element.