An integrated threat protection solution designed to detect, investigate, and respond to cyber threats across Microsoft 365 services.
Microsoft Defender is a separate app to the Defender that is pre-installed in Windows as part of Windows Security, if you have a Microsoft 365 subscription, then Microsoft Defender would also be installed as part of the Office apps installation, if you do not have any 3rd party anti-virus installed, you can then log into that app with the same Microsoft account and use it to protect your system.