Automobile exception refers to the legal principle that allows law enforcement officers to make searches and seizures on automobiles without a warrant if there is probable cause for believing that the automobile has evidence related to a crime inside it.
The automobile exception allows the Fourth Amendment to be temporarily suspended.
The reason why the automobile exemption exists is because sometimes, there is no time for law enforcement officers to get a warrant. In such circumstances, the evidence would likely be destroyed or relocated if police officers did not make searches and seizures on the spot, under the automobile exception.
For example, if a police officer pulls over a vehicle, and the officer sees that there are bags of cocaine in the back seat, they can make a legal search and seizure without a warrant because probable cause would exist. If the officer could not do this, the evidence would likely disappear by the time a warrant was obtained.