Scaled

Scaled[{xA, yA}]

represents scaled coordinates from 0 to 1 relative to the plot range of the Graphics expression (even if it is Automatic).

Scaled[{xD, yD}, {x0, y0}]

uses x0, y0 as normal coordinates and adds offset in absolute xD and yD.

It can be used as part of coordinates for various primitives such as Text, Line, Point, Disk and etc.