DVD

DVD (digital versatile disc) is an optical media storage format. In its most common usage, 'DVD' refers to a dic with video placed on it for public rental or purchase, although DVDs are also used to store personal media, on 'blank' DVDs - discs without any media on them - through use of a DVD Burner.

Leonard is, according to Sheldon in The Peanut Reaction, in need of a DVD burner. He is presumably still in need of one as Sheldon opted to buy him a wireless router instead.

Sheldon & Leonard are known to have a DVD player, in the pilot episode they discuss watching Battlestar Galactica Season 2 on DVD, with audio commentaries this time.