Or you want to know about the advantages?
Or you want to know if you actually even need this?
Using multiple monitors with one PC is a great thing: it can help lot of users to do much more than what they can do with a single monitor. In short, 2 more LCDs or LEDs etc with one PC is a Superb thing but only if the user Actually Needs This.
There will be no benefit for a user who just use PC for few minutes in a day to check email or to chat with someone etc.
On the other hand, if you are doing online jobs at freelancing sites or you manage your own website or create sites for other people or if you do any kind of online job or if you play PC Games or if you are using a Laptop and want to watch movies in a bigger screen, then multiple monitors is best for you.
You will be able to do more work with 2 or more monitors. You will be able to save lot of time.
1. Assume that you are doing online jobs at freelance sites
How much will multiple monitors help you?
It will depend on the type of online job that you are doing. For example, if you are doing data entry jobs, then you can open the Source file in the second monitor: copy the required content and paste it directly in the destination file which will be opened in the primary monitor. Add a third monitor and you will then be able to do this work quicker.
2. Managing websites
In order to run a website, one needs to do lot of stuff: like monitoring traffic, uptime, moderating comments, writing more content etc etc
You can open traffic stats tools in a browser in the left monitor: in the primary monitor, you can open MS Word or Openoffice to write articles and in the right/3rd monitor, you can open Dreamweaver or Photoshop or any other editing tool that you may often use.
3. Need for a Bigger Screen
Assume that you have a 15 or so Inch screen in your Laptop and you don’t have a Desktop PC. What if you want a bigger screen in order to watch Movies?
You can simply get a 22 inch or a bigger/smaller monitor and attach it to your laptop.
For this, you will need a Video Port.
4. Playing PC Games
Nowadays, a new way of playing games has been introduced. In one monitor, we can only see a limited area of a game, but if you add two more monitors, you can view a lot more area in your game.
Like if you are playing a Driving game, then 3 monitors will let you see cars that may try to pass from left or right hand side. Normally, we only see them if they pass us, but Nvidia 2d/3d Surround technology let us attach 3 monitors to play games like never before : )