A more thorough explanation:

A traffic stop is when a police officer pulls over a vehicle and detains the people inside. This is considered a seizure under the Fourth Amendment, which protects against unreasonable searches and seizures by the government.

To conduct a routine traffic stop, the police officer must have a reasonable suspicion that the driver is unlicensed or the vehicle is unregistered. They do not need to have a suspicion of criminal activity.

If during the traffic stop, the officer discovers reasonable suspicion of criminal activity, they may conduct a legitimate terry stop. State statutes may also provide legitimate grounds for traffic stop checks that do not require reasonable suspicion.

Some state cases have established that traffic stops conducted by government officials other than police officers may also be legitimate if they have reasonable suspicion of a violation of the law.

For example, if a police officer sees a car driving without license plates, they have reasonable suspicion to conduct a traffic stop. During the stop, if they smell marijuana coming from the car, they may conduct a terry stop to investigate further.

Another example is a state statute that requires all vehicles to have a safety inspection every year. Police officers may conduct traffic stops to check for valid inspection stickers without needing reasonable suspicion of criminal activity.