Microsoft Teams is a collaboration platform within Office 365 that allows for chat, calling, meetings, and file storage. It utilizes existing Office 365 services like Exchange, SharePoint, etc. and has dedicated apps available across all platforms. Guest access can be enabled to allow external users to collaborate within Teams. Administrators can configure guest access policies and permissions within the Office 365 admin portal. Teams provides capabilities for various business functions and scenarios including customer support, engineering, finance, HR, marketing, sales, and operations.