Normally, once you buy a domain name, it is yours for a year and cannot be canceled. The domain can be unregistered, say if it violates a trademark or copyright, and you don't want to be sued, but then you still have to pay for it.
However, if you contact HostGator immediately, there might be time to cancel the order before it is processed. In that case, we will be glad to cancel the registration, and no money will be taken. (If money is already taken, it is too late.)