What does it mean that a pan is "anti jamming"?
These pans (sometimes called chafing dishes) are designed to fit into a frame above water and a heat source to keep food hot. They are advertising that their pans won't get stuck (jam) in the frame. 

As evidence, see this video (and this), which shows how even after pressure is applied the pan does not require effort to remove from the frame. (I found the video here, on a tradeKorea page advertising a similar pan, and it was produced by an account called 'ChefPro'.)