How do you add a guest to Microsoft teams? How does a guest join a team?
If you are trying to figure out how to add an external member to a full blown team, not just a chat or meeting then below are some articles on how to do this.
https://docs.microsoft.com/en-us/microsoftteams/guest-joins
A team owner in Microsoft Teams can add and manage guests in their teams via the web or desktop. Anyone with a business or consumer email account, such as Outlook, Gmail, or others, can participate as a guest in Teams, with full access to team chats, meetings, and files. Only people who are outside of your organisation, such as partners or consultants, can be added as guests. People from within your organisation can join as regular team members.
By default, guest access is turned off. So, before guests can join a team, an admin must turn on guest access in Teams. To do that, use the link below…
https://docs.microsoft.com/en-us/microsoftteams/guest-access-checklist
If you are looking for general information on what microsoft teams is and how it works then the following video is pretty useful.