What does "zoning" mean for fighting games?

I've seen the terms "zone" and "anti-zone" used in regards to moves, as well as discussion about whether or not a character is a good "zoner" or has a good "zoning game."

What exactly does this term mean? Is it movement speed, avoidance ability, a combination of the two or something else?

Zoning: Intentionally keeping distance/pressure on your opponent, either reading their style or forcing them into playing a certain way. Adaptive to close combat situations and able to make good on big damage opportunities. (sic)
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A good zoning player will always create opportunities for themselves by keeping their opponent away from them as to gain control of the match, then adjust to their opponent's tactics/counters and act accordingly. (sic)
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Zoning doesn't have to involve repeated moves at all. Zoning isn't just keeping your distance, it's about keeping within a very specific distance, which may not even be a half screen away. It might be just barely within range of a normal move. The idea is to establish this distance and keep it, because it limits your opponent's options and allows you to react more easily, giving you the control of the match.

Source: http://www.trmk.org/forums/showthread.php/22827-The-Difference-Between-Zoning-and-Spamming