help what is a content locker??

Hi,

I've just been speaking to my aff manager over at ogads and he's been trying to explain to me for about 20 minutes what a content locker is and i still can't get my head around it. Hes telling me to promote one of there pre existing landing pages which offers free Instagram followers so what happens when a user clicks that offer, lets say i am promoting it via Instagram? Where does the content locking part come in to it?

Can someone please explain it to a dick like me lol?