Ipso facto means "by that very fact or act". In essence, it means that one thing happens as a direct result of another, that the result is known at all times, and that it is not of a surprise when it occurs. An example of this would be if a person ran over an animal with their car; the animal would be hurt, so they would say that the animal was hit and ipso facto the vet had to be called. This term comes up in all types of law and shows the intent of an action.
If something occurs ipso facto, then the person who committed the occurrence will be seen to be liable for the end result as though that were the result that they were aiming for. If a person gets shot and then dies, the person who shot them would be charged with murder, as the victim's dying was an obvious and known consequence of the shooting.