Scale in Miniatures is about size. People talk about Dollhouse scale, one inch, Half scale, quarter inch, Blythe scale, Barbie Scale, 1/6th, 1/12th, 1/24th, 1/48th/ 1/144th, then in the railway scale, G, O, S, HO, N, Z.
All of these relate to an item in our daily life converted to a smaller item in a ratio, of one inch to "x" inches. Why inches when metric is so much easier, it all started before metric became popular.
1:1 scale is what you have is the exact same size. From there in Miniatures things get smaller
So, in Doll House Scale or 1/12th a dinner plate measuring 12 inches across in our daily life would measure one inch across in a doll house. That same plate in Quarter Scale or 1/48th Scale ( which both happen to be the same scale, just called differently) would measure 1/4 of an inch.
In Dollhouses there are so many different scales it can take a bit of time to work it all out. The image below shows you the relative size of a couch in each scale starting at 1/12th.
There is a larger scale, 1/6th known as Play Scale or Barbie scale.
A standard 1/12th Dollhouse room would be 10 inches (254mm) deep by 12 inches (305mm) wide by 10 inches (254mm) high. In 1/48th scale (Quarter Scale ) the same room would be 2.5 inches (53mm)deep by 3 inches (64 mm) wide by 2.5 inches (53 mm)high.
In Railway models -see below.
Image of houses courtesy ofTheQuarterSource.com