Question

what is window defender​

Answer 1

Windows Defender is an anti-malware component of Microsoft Windows. It was first released as a downloadable free antispyware program for Windows XP, and was later shipped with Windows Vista and Windows 7. It has evolved into a full antivirus program, replacing Microsoft Security Essentials as part of Windows 8 and later versions.

Answer 2

$\bold{Window\:Defender}$ is an anti-malware tool that is designed to protect computer from viruses, spyware and other forms of malware.