Azure Active Directory Business-to-Business (Azure AD B2B) enables organizations to securely collaborate with external users by allowing invited guest users to access internal applications and resources using their existing credentials. The key benefits of Azure AD B2B include supporting users from any identity source, simple and secure access management, and enterprise-grade security for shared applications and data. Admins can invite guest users through the Azure portal or customize the invitation process using PowerShell and APIs. Guest users receive an invitation email to access shared resources after accepting terms and conditions. Conditional access policies and auditing capabilities provide control and visibility over external user access.