addprefix % ??

[David Holmes]

In the following:

JDKJRE_LIB_LIST := $(filter-out $(addprefix 
%,$(NOT_JRE_LIB_FILES)),$(ALL_LIB_LIST))

what does the % do as part of the add prefix? Does it literally add a % 
character? If so how is that then used? If I print out the variable 
there are no % values.

???

Thanks,
David