Ok kiddo, so you know how sometimes you see machines that have really long belts that turn different parts of the machine? Well, a Gilmer belt is one of those long belts.
The special thing about a Gilmer belt is that it has these little teeth on it that fit into grooves on the pulleys (that's what the round part of the machine is called). This helps the belt grip onto the pulley really well and keeps it from slipping around.
So, why is this important? Well, if the belt slips around a lot, it can mess up how the machine works and make it not do its job correctly. But if the Gilmer belt grips onto the pulley really well, then the machine will work like a charm!