Dragon Ball Z OVA is a collection of different animated series following the Dragon Ball Manga in Japan since 1986. However, before we move onto explain the existence of Dragon Ball Z, it has to be understood what OVA actually is. OVA stand for Original Video Animation, which are animated series and films that are specifically made for home video formats rather than being released in theatres or cinemas. Therefore, such animated series are not released in the theatres prior to the CD versions or the Blu-Ray versions. Dragon Ball Z is actually a sequel series to Dragon Ball. There are different OVA films and while they do not have an actual continuity, there are some films that actually do have connected storylines.
The company Toei animation produced different theatrical films; out of which four have been based on the Dragon Ball anime, whereas the other fourteen are based on just the Dragon Ball Z sequel. The 18th in the series contains stories from the chapters 517 and 518. The writer of the manga, Toriyama had been involved in this creation. The new film in the series which follows the Battle of Gods would be released in 2015.
There have been several theatrical releases as well along with some series filmed primarly for television. Funimation was the company that took up this series in North America. There are many fans that take these films to be theatrical but they actually are not, and this is the more interesting aspect. Initially, Dragon Ball Z was simply an OVA and then later on, it was turned into an actual movie. You also have to remember that OVA tend to cost more than the typical DVD. You have to remember that not all OVAs would have some closure. This trend has been extremely popular in Japan especially in the realm of animations. In fact, a lot of censorship issues that stories would face on the broadcast networks would not be faced through this method, which is why it initially became popular. It was also a cost-effective way to produce and then sell the series, and actually make a quick and lucrative profit. However, as far as Dragon Ball Z OVA is concerned, it served as a guide to the computer game. There were two volumes in the OVA series. This animation was also part of the video games. The complete OVA were then released in 2003. Therefore, to illustrate the video games in a much better way, the OVA of this manga were released.