Global mouse hook...what this means?

I´ve been alerted 4 times about opera.exe creating a global Mouse hook...what this means? Is this really any kind of attack, or a spyware?

 

Global hooks are used by many programs, Opera is probably using them for mouse gestures, you need not allow them but may lose some program functionality.
In the case of trusted applications that are on your protection list it should be safe to allow global hooks.

Pilli