There are two roles that control what you can do with Dot.
Admins can control the data model, data source settings and permissions.
Users can chat.
Roles are managed by admins on the Settings page.
User Settings page
Data Access Control
Groups manage who gets access to what. Users can access a table if they are in the same group (e.g. in sales).
A user can belong to multiple groups, a table can also belong to multiple groups.
By default all new tables get assigned the group all_users and new users get also added to this group. An admin can configure that new users don't automatically get assigned to this group if your organization operates rather on the "Need to know" principle.