The other things are self explanatory but Ownership plays a crucial role in the CRM Security Model.
Entities can be Owned by
1) Records of “Organization owned entity” can be viewed by the whole organization
2) Records cannot be shared or Assigned.
3) Organization entities have two access levels – None and Organization.
User or a Team
1) Records of “User or a Team owned entity” can be limited to users or teams, so that you restrict data access to authorized users
2) The user-owned or team-owned entities have five access levels: None, User level, Business unit level, Parent: Child Business unit level, Organization
Hope this helps.