I've never heard of this before, until earlier today but I am wondering exactly what it is.

When I have been on the computer for a while my eyes do feel tired and itchy, could that be CVS?

I've never heard it called computer vision syndrome, but it ispretty widely recommended that if you work on the computer all day that you take breaks to rest your eyes and sit a minimum of 18 inches away from the screen.

I found this definition in the Wikipedia:

CVS is caused by decreased blinking reflex while working long hours focusing on computer screens. The normal blink rate in human eyes is 16–20 per minute. Studies have shown that the blink rate decreases to as low as 6–8 blinks/minute for persons working on the computer screen. This leads to dry eyes. Also, the near focusing effort required for such long hours puts strain on ciliary muscles of the eye. This induces symptoms of asthenopia and leads to a feeling of tiredness in the eyes after long hours of work. Some patients present with inability to properly focus on near objects after a short duration. This can be seen in people aged around 30–40 years of age, leading to a decrease in the accommodative focusing mechanisms of the eye. This can be a setting for early presbyopia.

Though what you're describing could be simple fatigue. Anyone can get itchy and tired eyes if they stare into the computer screen for an extended period of time.

It's nothing too serious. All you have to do is work on making better habits. Try not to spend all of your time on the computer, and make sure that you take lots of breaks from looking at the computer screen.