Yes, as soon as you have selected the team members to share teams with, the group will automatically be created.
The group will then be visible on top of the list of "Recent Contacts" of Team members, the next time you want to share a comment.
Note: If you have created a group with a lot of team members, you can mouse over the names and see the entire name list. On the iPad, you have the same opportunity by clicking on the orange info icon to the right of the group.
You can create as many groups as you need with your team members. You can also add the same team member into several different groups.
Once you have created a group of team members, the team members that have been chosen into the group, will also have the newly created group stored in their own list of team members. This is an advantage if you or your colleagues regularly need to communicate with each other in the team, so that each of you don't have to create the same group to share your comments into.
You can read more about, how to share comments in this article: How do I share a comment?