Relative age allows scientists to know whether something is older or younger than something else, while absolute age means that scientists know the exact number in years that have passed since the object was created. Relative age will require the comparison of two or more objects, whereas absolute age does not.
Relative age comes up often in various fields, such as archeology. If archaeologists find a site with layers in it, they can make assumptions about the relative age based on the composition of materials in each layer. For example, if an area used for trash has modern refuse in it such as CDs and computers, and the layer underneath has cans made of tin, then it is safe to say the layer of tin cans have a greater relative age than the layer with modern refuse. However, this does not say anything about the absolute age of the layers. That is, scientists cannot tell exactly how old the layers are in years to the present date, only which is older than the other.
Techniques such as radioactive dating, including carbon dating, focus more on the absolute age of an object. An example of this type of aging includes rocks in Canada that scientists identified as being hundreds of million years old. Absolute age is more straight-forward and does not require any other objects for comparison.