Carbine??

What exactly is the difference between a carbine rifle and others besides it having a shorter barrel?

That really depends on the gun. Carbines were first developed as shorter rifles to be used by cavalry troops. They needed a lighter gun that handled more easily on horseback. So, some of those rifles were the same, just shortened with a saddle ring attached. If you look at an M-1 Carbine vs. and M-1 Garand however, they are totally different firearms. They have different actions, fire different cartridges, and have different stocks. If you look at an M-16 vs. an M-4 carbine, they are generally the same, but the M-4 is shorter and has a collapsible buttstock.