Internal users are members of your team that are within your company. They will be able to see administrators, other internal users, and external users. They do not have the same rights as an administrator.
External users are members of your team that are external to your company, such as:
External users will only be able to see administrators and internal users. They will not be able to see other external users. This means that if you are working with multiple clients, you can have them all on your team and they will not be able to see each other.
Note: The team option including internal or external users is only available for professional accounts.