To define access permissions on a repository item:
List - User or group has minimal permissions to view the item in the browser; display read-only property sheets and search for models.
Read - User or group has all the List permissions, and can also compare documents, and check the document (or folder contents) out from the repository.
Write - User or group has all the Read permissions, and can also check in, freeze and lock document versions.
Full - User or group has all the Write permissions, and can also manage permissions granted to users or groups and remove locks on documents.
Note that users who do not have any permissions on a document or folder cannot even see these items in the browser.