Contact Role

Can someone explain "Contact Role" to me a little.

It is a field that I see in my Contact Related Information under Accounts.   But it isn't a field that I can put on the Contact page?   That seems odd, so maybe I'm missing something.   It just makes sence that I should be able to modify that field via the contact page.  

The previous admin set up a field we call "Contact Type", which is essencially the same field.   So now, I feel that I have two fields in two different areas holding the same data.   I'm trying to figure the best way to clean this up a bit.