Each Field within an Object has it's own CRUD (Create, Read, Update and Delete) security permissions applied to it. Field level security settings can make the security applied to a field more restrictive for a User's Profile beyond what Object level security would on it's own, but cannot make the security less restrictive.
Each Object has CRUD (Create, Read, Update and Delete) security associated with it according to a User's Profile. In addition, each field within an Object has it's own CRUD security permissions on top of the Object level CRUD security. Field level security settings can make the security applied to a field more restrictive for a User's Profile beyond what Object level security would on it's own, but cannot make the security less restrictive.
