Team owners have the ability to invite anyone to join the team. With Microsoft Teams, team owners can easily add people by name. Team roles.

There are two main roles in Microsoft Teams:

• Team owner: is the person who creates the team. Team owners can make any team member a co-owner when invited or at any other time after they have joined the team. Having several team owners allows you to share responsibilities in the team setup. 
• Team members: are the people the team owners invited to join their team.

Team settings

Team owners can manage team-wide settings directly in Microsoft Teams. Included in the settings is the ability to add a team picture, set permissions on all team members to create standard channels and private channels, @mention the whole team or the channel, and use GIFs, stickers and memes.
The default channel, "General", is for team-wide announcements, discussions and resources, and will appear in all channels.

Private channels

Microsoft Teams private channels create priority spaces for collaboration within teams. Only members of the private channel can access the channel. Anyone can be added as a member of a private channel as long as they are already a member of the team. You may want to use a private channel if you want to limit collaboration to those who need to know or if you want to facilitate communication between a group of people assigned to a specific project, without having to create an additional team to manage. For example, a private channel is useful when a subset of people on a team want to discuss confidential information, or information specific to that subset, without the rest of the team being able to access those conversations and documents. A lock icon indicates a private channel.