Simplify the following text for a Grade 9 native English-speaking person.
Original: HD DVD ( short for High-Definition\/Density DVD ) is a discontinued high-density optical disc format for storing data and high-definition video .
Simplified: HD DVD , also known as High-Definition DVD , is an optical disc that is able to store large amounts of data , such as high-definition videos . It was considered to be the successor of the DVD .