People vs Positions/Roles

Does Dynamics CRM treat 'people' as separate entities to 'roles'? or are they just lumped together as 'contacts'? Obviously people change roles all the time, and we need to keep track of both (i.e. Where is 'he' now? Who is in that role now?)

How does Dynamics CRM manage this?

(I'm not yet a Dynamics user - just looking into what CRM tool we will adopt.)