>The images that you see on your monitor is the result of an illusion - an illusion created by the juxtaposition of tiny dots of red, blue and green. These three colors called the primary colors alone can create all the colors of this universe, thanks to the insensitivity of the human eye. Monitors exploit this to create all the 16,777,216 shades of colors supported by an operating system. However, they can rarely display the true colors of the real world. Instead they try to represent these colors as truly as possible. How close the monitors represents colors and brightness depends on how well the monitors are calibrated.
Monitors are usually calibrated as best as they can be at the factory before they are shipped to you. But prolonged use deteriorates the components within the monitor and it loses the initial calibration it came with. If you print photos on your computer or do graphical works like designing websites, creating logos etc, a badly calibrated monitor can ruin your work.
Monitors can be calibrated by using "test plates", which are sets of images with certain patterns and color diagrams on them. These test plates are viewed on the monitor to check how accurately these are displayed. Then necessary adjustments are applied so that these images appear as they should. Other calibration method involves the use of special hardware to make adjustments. These are specially for high end users.
A typical test plate
One easy method to calibrate your monitor is to use a software called DisplayMate. It's a shareware but the demo version is enough for most home users. The full product contains some extensive tests and adjusting involves opening up your monitor and making changes to the focusing magnet and coils! You wouldn't want to do that, so we will settle with the demo. The tests are self explanatory. Each test plate is preluded by a description of what you need to observe and what you need to do. At the end of the test, your monitor should be well calibrated.
There are several online calibration tools available as well. Checkout these: