Disc Tray
The actual physical operation of a DVD drive is fairly straightforward. Once the user has placed a DVD securely inside the disc tray with the data side facing down and the tray itself closed, the disc begins to spin. While this is going on, the drive's laser (which is used for accessing data and transferring it to your computer) points in one specific direction. The reason the disc spins so quickly is so that the laser can access all parts of the disc at once, thereby allowing minimal delay between attempting to access a file and the file actually being opened by your computer.

Data Track
The data itself is stored on a circular "track" that goes around the DVD the way grooves do on a vinyl record. All DVD drives can access discs with one layer of data. Drives produced prior to 2003 may have a problem reading and writing to discs with two layers of data. This is due to the fact that the standard specifications of a DVD drive's laser have changed over the years as technology has advanced. Newer DVD drives don't have this problem.

Speeds
DVD drives can access and write data at a number of different speeds. Writing to a disc at the lowest possible setting will make great strides in preventing any errors that may pop up in the burning process, although this is only really a concern for older computers. If the maximum speed of your drive is 32x, for example, that means that the drive can access and write data 32 times faster than real time. To simplify that, this means that if you're burning a movie file that is 1 hour, at 32x speed it's being burned 32 times faster than that hour it would take you to watch the file at normal speed.