While Base offers roles that provide access to either your own or the whole office's listing data, you can also configure users to have listing and contact access to other users' data. This is great for teams within an office. E.g. you can have a team leader that has full access to their team's data only.
Navigate to the user profile that you want to configure for additional listing & contact access
Under the account tab, make sure the role of the user is one of the standard user roles and not an administrator.
Click on the 'Portal & User Access' tab.
Now select which people this selected user has rights to. In the example below, the user will have access to Annali and John's listings and contacts and will be able to modify records: