A new way to interact with your colleagues has been introduced in Teams and is turned on by default: Video Clips.
Teams administrators can decide to turn it off by editing their corresponding Messaging Policy from the Teams administration portal (https://admin.teams.microsoft.com/) using the Messaging Policies blade (or Teams PowerShell)
Set-CsTeamsMessagingPolicy -Identity <messaging policy> -AllowVideoMessages $false
When turned on, end-users can then capture, send, and playback video messages in Chat a short video (1 minute maximum) – from any Teams endpoints – using the Record a video clip button available below the chat text field
NOTE this option may not be enabled for chat with external users