The Gibson Tun-o-matic bridge sometimes has to take a lot of punishment. Primary cause of this punishment is the strain of the strings pulling it down. Depending on how your guitar's set up, this can be substantial and, after a while, the tun-o-matic can buckle under the pressure.
The green line in the first photo shows the shape this bridge started out. The second image shows the same thing on another tun-o-matic (albeit a little less pronounced).
This collapse alters the radius that the strings are set to. The guitar's playability suffers and you'll often get a buzzing creeping in on the middle strings. Eventually, the bridge can develop cracks and fractures in places.
Gone too far, there's often nothing to do but replace the bridge. Sometimes, however, it's possible to get the original back to shape.
This is the Haze Tun-O-Matic Straighten-O-Matic. By clamping the bridge in this and applying careful, gradual pressure, it's often possibly to straighten out a collapsing tun-o-matic.
It's not magic—a lot depends on the extent of the collapse and the condition of the bridge—but, if you're lucky, it can save an original.