If you watch movies a lot on your comp, or do movie editing, you need a shuttle control. I don't do movie editing, but i do watch movies on my computer. (in fact don't own a TV since about 2000.) Shuttle control lets you control the speed of play, by how fast you turn the wheel. For example, suppose you have frozen the frame to enjoy slow motion of a kung fu fight or figure skating. With keyboard, you can forward one frame with a press of a button, and it is useless. The best you can do is to use the mouse to painstakingly drag the slider. That gets painful. Sure, you can use the pre-defined speed to play slow motion. And suppose you really want to see a particular 2 or 3 frames of how that kick is done… But then you have to rewind and re-click the whole thing. By all the buttons manual fuss, it already spoiled your mood to enjoy the slow motion.
This is where shuttle control comes in. You can watch sections in slow motion at whatever speed you want, forward or backward. The frames flow with the speed you rotate the wheel.
Jog wheel complements Shuttle wheel. It lets you change the direction of play in high speeds to positions you want. The more twisted the wheel is clockwise, the faster is your fast forward. Similarly, if you twist it anti-clockwise, you control speeds in backward direction.
Shuttle/Job control was popular with the VHS days. They usually are on the remote of expensive VHS players. Professional movie editing hardware always have it, still.
Though, i'm not sure the Contour Design's devices support your dvd player… in particular i don't know if it supports VLC, which is what i use these days.