Geologic time

 You some times hear scientis saing this two word relative age and absolute age and you dont now to wat they refer until today because i will explane you the diference of each one.
The diferent between relative age and absolute age is that relative age is the age that is no so much clear of some thing and absolute age is the age  that is a 100% sure that that is the age.

There are 4 types of Eras Precambrian, Paleozoic, Mesozoic, and Conozoic. And we live in the Era Cenozoic, Period Quaternary but I think that the chart below will  help you to understand more.