When creating your site with Ruby Datum, you will be asked whether you want to set up your site with user-based permissions or group-based permissions.
If you choose user-based permissions then all permissions on your site are set on an individual User basis.
If you choose group-based permissions then all permissions on your site are set on individual Group basis.
User-based and group-based permissions are set for each folder and file either on an individual basis or in bulk.
Users can be assigned to groups of your choosing whether your site has user-based or group-based permissions. However, if you choose user-based permissions then different users within the same group can have different permissions, but if you choose group-based permissions then every user in one group will have the same permissions.
Here is a quick video on how to setup the user or group based permissions: