I read there are different matrix type, such as:
Where in the specs would this be?
How can I find out if a monitor is TN or S-IPS etc?
Easiest way - Look for a sticker on the back.
Slightly harder - Look for the original manual or the box, may say.
Harder again - Google the model number and look at the specifications on the website.
Hardest - Email the manufacturer and ask them.
If you have the monitor in front of you, you can try to guess from its visual characteristics. Here are a few resources with visual information about various panel types: Wikipedia, PC Hardware Help TFT Central, AnandTech. You can also search the on-screen display, but the information is rarely present (sometimes it's present in a “hidden” menu that requires pressing several buttons together or for several seconds).
If you have a model number and want to know its panel type, you can check the monitor's documentation, but they don't always specify the panel type. You can search for technical reviews on the web. TFT Central has the information for a lot of models. HardForum has a list of S-IPS-equipped monitors, but it hasn't been updated in a while. Beware that some vendors change panel types without changing the model name (computer OEMs more so than monitor manufacturers).