Is a DVD driver the same thing as a DVD decoder?
A DVD driver is also a program that enables communication between your PC & DVD Player/Burner. While the Decoder program enables your PC to recognize the files on your DVD.
DVD is a compression format, a way to reduce data and still transfer what you need, & it is a physical storage format. Straight data (documents, pictures, sounds, regular movies) are non-compressed when burned to a DVD but a DVD movie uses compression to get more data on to the disk. A codec is what tells a computer how to compress the data; a decoder is just the part that reads the DVD movie info and turns it into pictures.
A driver is a piece of computer code that tells the operating system how to deal with a physical device - a drive, a screen, a printer, a mouse .. these all need drivers to translate the physical data from the device into a format the main machine expects. Without a driver you can run a decoder all day long, but it won't be able to read a disc so that it can show a movie. A driver without a decoder can only handle files and no DVD movie.
So, to watch a DVD movie on your computer you need a driver to read the disc and a decoder to turn that data into something useful (frames of pictures.)