A Binding is an edge edging at the neck, body and/or the head plate of a guitar. It has both visual and technical sense. First bindings look more nobly as no Binding and secondly the very sensitive sharp edges of an instrument are protected by the tenacious material fo the bindings – how fast has it happened, that one rubs the wrong way up with the guitar someplace? And one already has an extremely angry and ugly notch in the edge.

A Binding consists of material that is substantially harder than the material of the original edge. They are usually made of synthetic material (ABS or celluloid) or a hardwood mostly. This decimates the risk that smallest inattentivenesses result in bad gashes.
Here an example for an a little more effortful layered Binding:
It has 4 layers: Black/white/black/Perloid.
Right besides this a simple cream-colored Binding…

Some cheap guitar manufacturers only paint their Bindings on the edge – It really can happen with the time, that the paint flakes off by enemy contact – and then the whole looks extremely mangy (see second illustration). Who has seen an older instrument of these manufacturers before, knows what I talk about! And this shitty a binding can look if it isn’t 20 years old and just painted on. One can see very beautifully, there is no more paint directly at the edge but you see the wood lying under this — this wouldn’t have happened with a genuine binding! I have restored this classical music guitar, she was in a desolate state.