I'd imagine that ever since the invention of the sawmill, hardwood floors have been an essential part of homebuilding. Many houses built over the past couple of decades “feature” carpet over plywood or oriented strand board; when the carpet wears out, homeowners start thinking about something more durable, and hardwood flooring usually makes the short list.
In days of yore, unfinished “strip” flooring with tongue-and-groove edges (which hold the boards together and hide the nails) was your only choice. Now, however, you can buy tongue-and-groove prefinished. Although this stuff is extremely durable, there are fewer color options, and it's difficult to sand out high spots or damage during installation.
You'll also see a number of other ways to get a floor that looks like a traditional strip floor:
Engineered plank floor is hardwood veneer on plywood. One key advantage is that the planks are more stable. With changes in humidity, strip flooring swells and shrinks, but this stuff is supposed to be so stable that at least one manufacturer says it can go directly over concrete. One disadvantage is durability: Whereas you can sand a strip floor several times, giving a half-century or more of wear, sanding can be risky over the thin veneer.
Longstrip flooring is like engineered plank flooring, except each separate piece actually looks like several strips. The occasional joints across several strips are a dead giveaway that this is not strip flooring.
Laminate flooring is a wood look-alike (more or less). A plastic film is printed with a wood pattern and glued to a backing. Quick to install, and said to be tough, it's not something you'd want to “fix” with a floor sander! But it does have major advantages in terms of easy installation. See Step 7: Laminate Flooring Installation at the end of this guide for details.