Colour gamut or colour space refers to the range of colours which the screen is capable of showing, in relation to a reference colour space. The human eye can see a certain range of colours which is represented by a CIE Diagram. This shows the full range in reds, greens and blues which the eye can see. Within that massive range there are various reference colour spaces, the most common of these being the sRGB space. There are also other reference colour spaces such as the NTSC and AdobeRGB which are often used in specifications nowadays. These are larger colour spaces than sRGB, so manufacturers needed a way to quantify the improvements they had made.
The colour space / gamut capability of a monitor is not determined by the panel technology, but rather by the backlight technology being used. Traditional screens used standard CCFL backlighting which (for simplicity of comparison here) offered a colour space covering the sRGB space almost exactly, which equates to about 72% of the now popular NTSC reference space. With backlighting technology improvements, some screens now use W-CCFL (Wide) backlighting which can offer an extended gamut covering around 92% of the NTSC space. Other technologies like LED backlighting are also becoming more common, and cover >100% of the NTSC space commonly.
While a larger colour space might sound like a good idea, it's not always for everyone. You need to keep in mind what content you will be viewing on the screen, and what colour space that content is based on. Since sRGB is very common and the standard for many things like Windows and the internet, viewing sRGB content on an extended gamut screen can cause oversaturation of colours. Reds and greens in particular can appear quite 'neon' and some users do not like this. The smaller colour space of the content is, in a very crude way, 'stretched' over the larger colour space of the monitor. On the other hand, some applications are colour space aware (eg photoshop) and so if you are working with extended gamut content, you will prefer an extended gamut screen. I'd certainly recommend reading more into this as it is only a brief summary here. Where a screen has an extended gamut, they sometimes provide an sRGB emulation mode which work to varying degrees. Handy if you might need to use it, but make sure the screen offers a decent performance when in this mode and that it works.
