In the LEGO community, "Minifig Scale" is a term for LEGO constructions that are on a scale comparable to that of a LEGO minifig. Since a minifigure is about 4 centimeters tall, and a typical person is around 1.65 meters tall, minifig scale would be around 40:1. As far as I can ascertain, LEGO has never made an official pronouncement on this, in part probably because the proportions of a minifig are quite different than the proportions of an actual person. Among the more technical-minded of the LEGO community, there is some debate about what Minifig scale would be, as you can imagine.
Most official LEGO releases are in minifig scale, especially in what is the "core" line of the themed LEGOLand sets, including the town, space and castle themes. The biggest exception to that is probably the LEGO Architecture line, which includes landmarks like The Eiffel Tower. Most user creations, whether casual or serious, are also at minifig scale, although there are exceptions to that.
Even within official LEGO releases, there is some flexibility in what minifig scale is. For example, most of the LEGO town sets include cars that can fit exactly one minifig. LEGO also has more realistic car sets that would be proportioned more realistically to the included driver minifig. Like with most modelling, there is an amount of abstraction that you just have to accept, instead of asking why Goofy is a dog and has a dog, too. LEGO sets, after allowing for some abstraction, keep a pretty consistent and realistic scale.