Red notification badge on the Teams icon in the Dock. You can switch between Teams vs MacOS notification settings but to allow the dock icon option, you'll need to activate the MacOS notifications for Teams.
Some folks prefer the red numbered notification badge that pops up on application icons in the MacOS dock verses the audible 'dings', buzzes or banners that may be more intrusive to your daily work.
Microsoft Teams allows for various notifications settings controlled either by the Teams application itself or through the MacOS.