What is the difference between an Admin, an Owner, and a Primary Contact?

Admin and Owner are permission levels that end users can have in the web application. The Admin is the highest-permission role and there can only be one Admin user per Company. The Owner role is similar to the Admin – it can add/remove other users, add/edit/delete devices/alerts/reports and sensor maps, and delete Locations. An Owner cannot delete the entire Company (this is reserved for the Admin).

Please see this article for more on user permission levels

A Primary Contact is not a permission level but instead the contact(s) who will be suggested as default recipients for any alerts and reports associated with that Company/Location.

A Company/Location can have any number of Primary Contacts (including zero).