What is the difference between plasma TV & lcd TV

They're actually different technologies. A "plasma" is very different from an LCD (Liquid Crystal Display). LCDs require backlights to shine through the LCDs in order to get a picture. Plasmas emit their own light. There are differences in the intensity of color, etc.

Let me google that for you - Plasma vs LCD TV (http://www.lmgtfy.com/?q=Plasma+vs+LCD+TV)