Final answer:
Microsoft Teams supports three primary identity models: Internal, which uses an organization's IT infrastructure; External, which manages guest user identities outside the organization; and Hybrid, which combines internal and external identity management.
Step-by-step explanation:
The three identity models that Teams support are Internal, External, and Hybrid. These models define how a user's identity is managed and authenticated in the Microsoft Teams environment. The Internal model refers to identities managed by an organization's own IT infrastructure, often via Active Directory. The External model is for guest users who have identities outside of the organization's IT infrastructure, which might be managed through services like Azure Active Directory B2B. The Hybrid model combines both, enabling identities to be managed both internally and externally, giving organizations flexibility especially when dealing with various types of users.