As flat-panel televisions gain in popularity, many consumers are still trying to figure out what's what. Following are a few concepts and definitions.

Don't confuse flat-panel televisions with flat-screen TVs. Most box-shaped televisions have flat screens these days, not curved ones. Always go for high-definition versions if you are going to invest the money.

Types of flat-panel TVs

* PLASMA

How it works: Charged electrodes between glass panels cause tiny pockets of inert gas to change to a state of plasma. This process causes ultraviolet light to be produced, which reacts with the red, green and blue phosphors in each pixel to produce visible light.

Life expectancy: 30,000 hours (10 years at eight hours a day). Gases can't be replaced.

Largest screen readily available: 61 inches

Starting price: $4,000 for a 42-inch screen

* LCD

How it works: A light bulb behind the panel shines light through the display like a digital watch. The liquid crystal diodes align so light cannot pass through them.

Life expectancy: 60,000 hours (20 years at eight hours a day) with the original bulb. Light bulbs can be replaced.

Largest screen readily available: 37 inches.

Starting price: $450 for a 13-inch screen

Sources: www.plasmatvbuyingguide.com; lcdtvbuyingguide.com