HELP!! How does the ground wire trip the circut?

I know that the grounding wire is attached to a grounding rod and transfers the current away from an appliances which becomes live on its outer casing ect. But im confused on just how the whole circut operates. Just how is the circut tripped when the appliance mullfanctions like this. Is it because the resistance in the circut is almost 0 therefore the amperage that flows through the hot wire is very large and so blows the fuse/circut breaker? PLZ HELP !