Handbrake is a program that reads video files (from a DVD or the file system) and writes out a transcoded file stored in the filesystem. It's one of these swiss army knife all-purpose programs with can do a lot of things in a narrow area of functionality. We use Handbrake to convert DVD representations of video into MP4 representations. We also use a similar program, VLC, which has even more functionality.
Who could dislike a piece of software aimed at the Jimmy Buffet generation? When the program finishes transcoding a DVD, it issues the following alert: