You've seen the advertisements and you're intrigued: Is now the time you should take the plunge and buy one of those new high-definition televisions that promise to dramatically improve your home video experience?

Based on price alone, these sleek, rectangular sets -- some so thin they can hang on your living room wall --have dropped dramatically in price since last year, according to the Consumer Electronics Association.

It's now possible to buy a 42-inch plasma flat-panel set, which is the most popular size in TVs that can be wall-mounted, for less than $3,000, compared to $8,000 or more for the same set two years ago. Other high-definition sets can be purchased for well under $2,000, though a buyer might have to settle for a smaller screen and an unfamiliar brand at that price.

But before you get in the car for a quick spin to the electronics outlet, you can save yourself time, aggravation and, most importantly, money by learning a little bit more about this brave new TV world.

A lot has changed since you bought your 32-inch analog set 10 years ago. There's a dizzying array of new terminology -- DTV, SDTV, HDTV, EDTV, DLP, LCD -- and it's possible to spend thousands of dollars and still not get what you want.
Here's what you need to know to be a savvy TV buyer:

What's the difference?
It's all about the sharpness of the picture. That's determined by the number of horizontal lines on the screen and the number of pixels -- the color dots that make up the picture -- in each line.

The analog TV sets we grew up with and still watched in a vast majority of homes are capable of only displaying 480 lines with 640 pixels per line -- the benchmark called standard definition (SDTV).

The best of the digital high-definition TVs are capable of displaying 1,080 lines with 1,920 pixels per line, but sets that display 720 lines and 1,280 pixels also are called high-definition.

The reason there are two levels of high-definition TV has to do with programming. About 70 percent of broadcast television is available in high-definition, but not all of that high-def content is broadcast at the maximum resolution.

Even at the lower level, a high-definition TV picture can be like looking out your living room window, the colors and details are so crisp.

But buying a set isn't simply a matter of telling the salesperson you want a high-definition TV and then slapping down your credit card. That would be like walking into a car dealer and saying give me something with four wheels and an engine.

Basics of digital TV
Digital television, or DTV, is the bedrock of TV's future. In 1997 Congress passed a law that said the U.S. broadcast TV industry must switch from analog to digital signals. Digital signals, which use the ones and zeros of computer language, allow broadcasters to send programs with higher definition pictures or to split the signal to send multiple shows on the same channel.