Hide an internal job from some users
To keep an opportunity away from certain users, give it its own opportunity type and set that type to None for those roles.
Go to Settings > BASIC SETUP > Jobs & Opportunities and add an opportunity type for the internal work, for example "Internal".
Go to Settings > SECURITY > User Roles and open the role.
Under Opportunities, find the opportunity type and set it to None.
Save the role.
Each opportunity type has its own setting for each role, so users can keep full access to other types. The main Opportunities setting always shows the lowest level of any type.
Limit access to documents by type
Roles can also control access by document type: a document type set to None means users with that role cannot view or upload documents of that type. Activity types work the same way with levels from None to Full.