what is the effect of a percentage sign (%) as last character on the command line

[Peter <vmail@xxxxxxxxxxxxx>]

Hi

What exactly is happening when I say

$ <anycommand>%

( a percentage sign as last character after any command) resulting in no 
output , whereas

$<anycomand>%<space>

results in normal output

for example:

$date%

(no output )

whereas:

$date%_    #   the underscore means a space char

Thu Jan 21 11:33:48 CET 2010


I can't figure which meaning of the percentage applies in this case ( % 
process number with number omitted, % integer division , % special file 
expansion, ... )

Most probably a very stupid question, sorry, but I just cannot 
understand this behavior ...

Thanks
Peter