What is spy detector app?

Excuse me, could you please explain what a spy detector app is? I've heard of it being used to detect potential threats on mobile devices, but I'm not entirely sure how it works or what features it typically offers. Is it a type of security software that scans for malicious software or hidden cameras? Are there any specific benefits or drawbacks to using one? I'm particularly interested in how it can help protect my privacy and personal information.