Simplify the following text for a Grade 10 native English-speaking person.
Original: The British Rail Class 332 ( originally Class 331 ) is the type of electric multiple unit train used on the Heathrow Express between London Paddington station and Heathrow Airport .
Simplified: The British Rail Class 332 is the type of electric multiple unit train used on the Heathrow Express between London Paddington station and Heathrow Airport .