Microsoft Teams is an application that is part of Office 365. You can use it to communicate (chat, audio, video), access your business (team) data and connect to other Office 365 applications. You can also connect to all kinds of external (cloud) applications, such as Trello, Asana, CRM, etc: Trello, Asana, CRM, PowerBI, Jira, and so on. Microsoft Teams is a hub for your daily work, communication and collaboration with others.