If you suddenly find that your car sounds particularly loud when you accelerate and the noise is coming from the exhaust then you most probably have a hole. This can not only be embarrassing and could actually get you in to trouble with the police if it is too loud, it can mean that your car fails an MOT and is therefore not roadworthy.
So what options do you have? Depending on where about the hole is in the exhaust and how big it is, you could try repairing it. Some garages offer this as a service where they will weld a patch on or you can actually buy exhaust bandage that you can apply yourself to cover up he hole. Both of these methods are somewhat temporary although the garage option is definitely designed to last longer. You need to weigh up if it is worth repairing it or replacing it as if the exhaust is relatively old anyway, you may find that you develop another hole in the next few months and therefore would be better to replace it.