Okay kiddo, you know how cars have license plates with numbers and letters on them? In Ireland, those plates are called "vehicle registration plates" and they help the government keep track of which cars are on the road.
The plates in Ireland have two letters, followed by - which means "space" - three or four numbers, and then another two letters. The letters at the beginning and end of the plate show which county the car is from, like "D" for Dublin or "C" for Cork.
The numbers in the middle are unique to each car, so if you see a car with the same letter combination in a different spot, it's a different car. There are some special plates too, for things like government vehicles, taxis, and vintage cars.
When you register your car with the government, they give you a plate to put on your car. You have to keep that plate on the car all the time you're driving it, so the police know that you're allowed to be driving that car.
And that's it! Vehicle registration plates in Ireland are just a way for the government to keep track of which cars are on the road and where they're from.