The reload glitch is basically a way to shorten the time required to reload your weapon. I remember a TGer made a video documenting this and posted it in the BC2 forums. The way it works is you start reloading your weapon and before the animation completely finishes you switch to another weapon and then back really quickly. It will go back to your first gun which is now fully reloaded. If you do it too early in the animation it will make you reload again. It doesn't seem like a very big deal to me because it saves you maybe one second and I would not be surprised if everybody here has done it at one time or another by accident. For instance, let's say you're reloading your primary weapon when an enemy stumbles upon you at which point you frantically switch to your pistol to defend yourself. If you happen to survive that fight, when you switch back to the weapon you were reloading you might happen to find it is fully reloaded even though you cut it off during the reload animation.