Does windows security need to run in background

Windows Defender automatically runs in the background, scanning files when they are accessed and before user open them. When a malware is detected, Windows Defender inform you. It won't ask you what you want to do with the malicious software it finds.

Windows Security always runs in the background unless you force stop it.
It boots up when you turn your pc on just like any other antivirus system.

Ihave never used that feature before but i think it's true