What is Microsoft Teams App?
Also called Teams Bot, Teams Integration.
A Microsoft Teams app is a package installed into a Teams tenant that can add a conversational bot, tabs, message extensions, or interactive cards. It is described by a manifest, distributed through an organization catalog or the public store, and governed by tenant administrators. Identity and permissions come from the organization's directory.
The manifest declares which capabilities the app adds and which permissions it needs. A bot exchanges activities with the Teams service, tabs embed a web page inside a channel or chat, and message extensions let people invoke the app from the compose box. Adaptive Cards provide structured, interactive content that renders consistently across the Teams clients.
Distribution is an administrative decision. Tenant administrators decide which apps are allowed, who may install them, and whether they appear for the whole organization or a subset. Because identity comes from the organization directory, an app can align its permissions with a user's existing access, which is one reason these apps are common in regulated environments.
Teams behaves differently from other chat platforms in ways that catch teams out. Scope matters, since personal chat, group chat, and channel each expose different context. Meetings add their own surfaces, including in meeting panels. Client differences between desktop, web, and mobile show up in card rendering, so anything visual needs checking in each, and administrator policy can block an app that works perfectly in development.
For assistants, the meeting surfaces are the distinguishing feature. An app can participate in a scheduled meeting, present content inside it, and act on what happened afterward, which connects the chat channel to the calendar and to meeting records rather than treating them as separate systems.
Key points
- Declared by a manifest and approved by tenant administrators
- Capabilities include bots, tabs, message extensions, and cards
- Personal, group, and channel scopes expose different context
- Identity and permissions come from the organization directory
- Card rendering differs across desktop, web, and mobile clients
In practice
A finance team installs an approvals app. When a purchase request arrives, the app posts a card into the finance channel showing vendor, amount, and budget line, with approve and query buttons. Approving updates the card in place so nobody approves twice. The same app adds a tab listing open requests, and the tenant administrator has scoped its installation to the finance department only.