importance of variable type in programming

[MehrdadSComputer]

Hi thereall
I need some info about importance of variable type in programming,
I need to know different between "floating point" and "fixed point" .
for example different between speed of programs when using "fixed point" or "floating point

[kbw]

http://en.wikipedia.org/wiki/Type_system

[Computergeek01]

Floating Point = Variable percision (mostly).

Fixed Point = Set percision.