Variables

Variables are placeholders that will be substituted with values when the application runs.
When you see womething like this:
"Error: file $s causes error $s"
Both of the $s will be replace during execution to produce an error such as this:
"Error: file /home/bob/todo caused error segmentation fault"

Changing the order

You language may change the order of sentences.  In this case feel free to change the order 
of the variables.  However in your translation you will need to tell the computer
what new order you have used.
Eg "Xxxxx $2s xxx xxxx $1s"
Will reorder the variables placing the second $s before the first.

Variable styles

There are many different types of variables the most common are the printf style which 
include the following: %s %d, etc TODO

You will also see these
%PROGRAMNAME (OpenOffice)
%PROGRAMNAME%
$file
$file$
$1