What is a 'Container' in a GroupShare context?

I'm trying to create a TM in GroupShare and have followed the "Creation wizard for a new translation memory".

However, at the final stage the "Finish" button is greyed-out. I suspect this is because the "Container" field has been left empty.

I've looked around and found that our GroupShare installation doesn't yet have any containers defined, and that I can define these in the Infrastructure section.

But this brings about two questions:

  1. What is a container in this context?
  2. I'm unable to create a container because the "Database server" drop-down doesn't offer anything to select.

I've added a database (which I called "Default" and which I pointed towards the same DB on which GroupShare is already running), and then attempted to attach a container to this. But it tells me

    Cannot find configuration data for [whatever I enter in the "Database Name" field] - this is not a TM Server database/container
    Invalid object name 'dbo.parameters'
    --> Start upgrading Database Schema from TM Server 8.05 to 8.06...

It looks like my lack of understanding is restricting me here. Can anyone shed any light on this situation?