Groups represent a set of Microsoft 365 Users that can be targeted as part of a call flow. These are the same Groups that are used elsewhere in the Microsoft platform.
To create a new Group, navigate to the Groups page using the left hand side menu item. Select Create Group at the top. This will show a modal window that requires a name and the initial set of users in your group.
Groups created via the portal are always Microsoft 365 Groups. Multiple users can be selected, use the drop down to select the users one by one.
Once the Group is created it's possible to edit the name and amend the group users by clicking the Settings Cog button on the end of the Group row.