You can be sure that you will be able to understand the cycle of these birds very easily as it is one of the most simple cycles around. The life cycle of the peacock is broken down into these certain categories to label the stage at which the bird is at within its life.
When a peacock is at the juvenile stage, they are nearly going to be the same size of the adults and will almost look the same, however they are not going to be at the stage where they can reproduce, and this is what separates the adult birds from those which are younger.
You can be sure that you are going to be able to tell the adult birds from the younger birds as the colors of the feathers are going to be different, and this is very noticeable with regards to the male peacocks as they are the ones which have the predominant tail features which make the birds so different and popular. If you are studying the birds or if you are simply interested there is no doubt that you are going to be able to understand the lives of these birds.