Some powers create zones, and most of them just say it, "zone", but what exactly is it? I mean, whats the size? For they just mention the range of where I can put the "core" of the zone!
Whatever area the power affected is the area encompassed by the zone.
Almost all zone powers are close or area powers, allowing the zone to cover more than one square, though there are a few ranged zone powers that create a zone affecting a single square.