Yes, along with other security measures, Windows Defender is an antivirus programme. What's more, it is a good one which means that the need for a third-party antivirus programme to be installed on your computer is greatly diminished. It should protect your PC from other nasty things, like spyware, too.

Defender is a free-to-download piece of software that was developed by Microsoft for use by any of its customers who are running a licensed version of their Windows operating system. It was based on a system first developed by the GIANT Software Company.

The Windows operating system provides Microsoft Defender free of charge to all its users. Users of Windows operating systems receive Microsoft Defender at no additional cost since it integrates with their system update process. Microsoft Defender delivers complete security protection while remaining totally free from charges that are common in other free antivirus solutions without premium upgrades. The Windows Security suite automatically updates its components, including Microsoft Defender, and makes it available for free to all users.