TV technology just keeps marching on. In 2008, only 34% of American households owned a high-definition TV set. Today, even the smallest and cheapest TV available in your local electronics store comes with a modestly high-def 720p screen. And the basic HDTV sets are being squeezed out by an even higher-definition experience. Say hello to the 4K TV, also known as Ultra HD.

What is a 4K TV?
At a basic level, a 4K TV set simply presents a lot more visual information on the screen than your old HDTV set, much like how HDTV offers a superior viewing experience over standard definition TV (if anyone remembers those relics).

4K or Ultra HD compared to a few older standards. That's how much larger your next TV can get without losing fine-grain detail. Image source: Public domain-licensed Wikimedia file, lightly edited.

Let's assume that the current TV standard lands at roughly 1080 pixels per vertical line. Many signal sources don't actually offer this quality, but hold your horses -- the TV set can probably handle it. That's full HD quality, up from the 480 pixels per line in standard definition and 720 pixels in lower-grade HD signals.

4K TV can handle 20160 pixels per vertical line, and also twice as many color dots on the horizontal plane. Hence the "4K" moniker, since this signal offers four times as many pixels as the baseline standard it replaces.

But wait -- there's more.

In the 4K TV signal, you'll also find a lot more color information. Standard and high-def TV sets and their incoming signals have so far supported so-called "true color," which works out to nearly 16.8 million possible shades. While impressive, you'll still notice bands of awkwardly digital patterns at times, such as in single-color shading or very dark scenes.

The color space used in 4K TV signals allows for much more nuance, covering billions of unique colors. Bye-bye, gnarly shading progressions and hello, detailed scenes in the dark.

Moreover, the moving pictures are moving faster. Standard definition maxed out at 24 frames per second and HDTV can go as far as 60 frames per second. 4K TV handles all of those speeds, but can also run at 120 frames per second.

So, yes, there's a real visual difference, and, no, it's not all about increasing the pixel count. That's certainly a start, and will help enormous screens presenting ultra-fine detail, but the extended color space and quicker refresh rates also matter.

Can I afford it?
In short: Yes, you can.

4K TV prices are dropping dramatically. In 2013, a 55-inch 4K TV would have set you back some $4,000. Today, several 4K sets of that size sell in the $800 range -- and that's before the Black Friday 2015 rush and other holiday discounts.

And in the lower price ranges, 4K TV is coming on strong. The most affordable 4K sets now start at less than $500. That's still about twice the price of a similarly sized HDTV screen, so the new technology isn't a free add-on quite yet. But we're getting there, and fast.

Image source: The Consumer Electronics Association.

Can I use it?
OK, so here's the trick: There really isn't a ton of 4K-quality content available yet. For now, it's mostly a future-proofing technology that set syou up for the day when true 4K TV signals really hit the mainstream.

Blu-ray players generally don't offer anything beyond a 1080p HDTV signal. It's coming, but it'll be a long and slow process before your average Blu-ray disc even ships with a movie in 4K-level formats. The first 4K Blu-ray players have started to show up, but that's just the first step. A full 4K movie needs the extra legroom afforded by larger-capacity Blu-ray discs, which may not be readable at all in plain old HD Blu-ray players.

So the hardware and content people are walking a fine line toward universal 4K Blu-ray support. The content can't move up until the supporting hardware is ready, and moving too fast will alienate users of current-generation Blu-ray players.

Online services are a very different story. Not bound by rigid hardware distribution limits, they can simply pump up their signal quality, balance it with more efficient data compression, and send it out to our bulging broadband pipes.

Netflix (NFLX -0.51%) was first in line with several of its original shows offered in 4K SuperHD quality. The company is also working with movie and TV studios to procure higher-quality versions of older material. Ironically, that's mostly material created on good old celluloid film, which offers image quality far beyond 4K or even the upcoming 8K levels. Content created with digital cameras and computerized cutting rooms, well, they are limited to the quality of their original formats.

According to Netflix enthusiast site Instantwatcher, Netflix currently offers 5,700 of its 7,200 movies and show seasons in 4K video quality. It's what you expect from Netflix nowadays, though these streams require a truly high-speed broadband connection and a high-end Netflix subscription.

Amazon.com (AMZN -1.14%) also offers 4K video streaming under its Prime Video service. This quality upgrade got started last December, and Amazon's 4K library is nowhere near as exhaustive as the Netflix catalog. But give it time, and you'll eventually see Amazon catching up.

In days of yore, you typically needed an extra set-top box in order to connect that flashy 4K TV set to a suitable online video stream. These days, so-called smart TVs are commonplace and you should really expect a new 4K set to come with apps for Netflix, Amazon Prime Video, and more. Hook the TV set up to your Wi-Fi network, sign in to your favorite video service, and start clicking.

Is it inevitable?
 4K TV is coming as surely as the HDTV standard did before it or cable boxes and color TV before that.

TV set makers are looking forward to another wave of hardware replacement, and the Consumer Electronics Association expects 4K Ultra HD to become the most popular TV format as early as 2017.

Meanwhile, Hollywood is getting ready for the quality upgrade. Hit shows like Game of Thrones are already shot and edited on 4K-quality hardware, but the high-definition TV broadcasts are limited to 1080 HD. In many cases, today's HD stations only run 720-pixel horizontal lines through your cable box, no matter how detailed the original may be. In some cases, moving to 4K TV will be as easy as flipping a switch to recode at a higher quality. In other cases, many show crews will need better cameras and editing boards in order to keep up with the times.

But it's all going to happen in due time. 4K TV is coming, and it's here to stay -- at least until the 8K revolution clears the table again.