Chat allows private conversations between an individual or group separate from the public Team channel. Chat also enables you to share files and to make video or audio calls directly to all members of the chat.
Chatting in Microsoft Teams
While in the Chat tab, select the person or group you would like to chat.
In the upper right hand corner you will see a camera button, a phone button, and a screen with an up arrow button.
The camera button will call the contact(s) using Video calling.
The phone button will call the contact(s) using audio only.
The button with a screen and an up arrow is used to share your screen with the contact(s)