Barring some technical details, using
\usepackage{geometry}% http://ctan.org/pkg/geometry
\geometry{hscale=<hval>,vscale=<vval>}
is effectively similar to
\geometry{totalwidth=<hval>\paperwidth,totalheight=<vval>\paperheight}%
thereby scaling the "total body" with respect to the stock/paper size. Technically, the "total body" could include the space around the text block, which includes the margin space (horizontally), header and footer (vertically), so the above is a small simplification.
Compiling the following minimal example, removing the appropriate comment, you'll notice the same look output by geometry
:
\documentclass{article}
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\usepackage{geometry}% http://ctan.org/pkg/geometry
\geometry{showframe,hscale=0.6,vscale=0.5}% First compile (left image)
%\geometry{showframe,totalwidth=0.6\paperwidth,totalheight=0.5\paperheight}% Second compile (right image)
\begin{document}
\lipsum[1-5]
\end{document}
The image on the left contains the hscale
and vscale
options, while the image on the right contains the equivalent totalwidth
and totalheight
settings:

There are many equivalences between options that can be specified. For example, noheadfoot
is equivalent to specifying both nohead
and nofoot
. These equivalences are usually meant to provide abbreviated package options (that combine other, more specific, choices) and promote ease-of-use.