The $ is used in formulas and other expressions to indicate an *Absolute*
reference as opposed to a *Relative* reference to a cell. Relative references
change when copied from one cell to another, and this is how Excel works by
default. Absolute references do not change when copied from one location to
another.
BTW- No offense, ww, but in the last line of your reply,
<<If you use =A1*$B$1 it would copy down as A1*$B$1 yet.>>,
as the expression is written here, the reference to A1 *would* change to A2,
A3, A4, etc., although the reference to $B$1 would, as you say, remain fixed
on that specific cell.
HTH |:>)