The World of Dragon Ball Z is a 20-minute OVA special that was produced and distributed by Funimation in 2000, narrated by Christopher Sabat. This OVA reviews the Dragon Ball series, beginning with the Emperor Pilaf Saga and then skipping ahead to the Raditz Saga through the Trunks Saga (which was how far FUNimation had dubbed both Dragon Ball and Dragon Ball Z at the time).
Two different English dubs are featured in the OVA: the BLT/Saban dubs of the Emperor Pilaf Saga, Saiyan Saga and Namek Saga; and the Funimation in-house dub of the Frieza Saga and Trunks Saga. This is because Funimation had not re-dubbed the early episodes of either Dragon Ball or Dragon Ball Z with its in-house voice cast at the time this OVA was made.
The World of Dragon Ball Z is featured on Madman Entertainment's DVD "Trunks - Z Warriors Prepare", as well as all of FUNimation's Androids Saga DVDs and the 2001 DVD release of Bardock - The Father of Goku.