It binds to completely different location, known as the allosteric site. Now, since the two sites, the allosteric site and the active site, are different, the inhibitor can bind to the enzyme regardless of whether the substrate is actually bound to our enzyme or not. So if we look at the following diagram, we have the enzyme shown by this brown region. We have this active side, we have the substrate shown in blue, and we have this inhibitor shown with our purple color. So this here is the allosteric side to which our inhibitor will bind, and this is the active side. So what this means here is the inhibitor can bind to the allosteric site regardless of whether this blue molecule, the substrate, is actually found inside that active site.