Relative Dating and Absolute Dating are two types of such techniques which are under practice to determine the age of the fossils, objects or civilizations.
The relative dating is the technique in the Geology through which the age is determined with relation to the other objects.
According to "Enchanted Learning," archaeologists use three main types of fossil: the true form fossil, trace fossil and mold fossil; a fourth type is the cast fossil. These fossils are made of an actual plant or animal.
The hard parts of the body like the bones or stems were trapped in rock and effectively preserved.
The absolute dating is more reliable than the relative dating, which merely puts the different events in the time order and explains one using the other.