Wide XGA refers to a set of resolutions used by display manufacturers that are non-standard, yet very common. Basically, these resolutions widen the Extended Graphics Array (XGA) standard to widescreen format. It is commonly used in LCD monitors and television sets. There is no specific resolution that applies to WXGA more than any other, but they aren't too hard to spot. For a television, the image is generally 1366 pixels wide, so if you have seen 1366x768 resolutions offered by LCD televisions, then they support a non-standard WXGA resolution.
As for laptop computers, the images are generally 1280 pixels wide as that is quite a common resolution for computing. WXGA is most commonly used with laptops that have a 16:10 display, with a resolution of 1280x800 pixels. There are many other variations on that resolution for laptop.