When you add new B2C Commerce users (for example, Business Manager users), you can assign roles to those users that restrict access to only those B2C Commerce tool modules they need to do their jobs. Within B2C Commerce tools, with the appropriate permission you can:
When viewing the list of users (select Administration > Users, click Find). You can see (if you are the administrator) the last time a user logged in, the number of days since then, in the instance's timezone.