What does "signature" in source packages means
 

Hello all,
many times, when looking for some source for softwares e.g "gaim", i saw "signature"
written in the braces.....
what does it mean..?

thnx.
regards

it can let you verify you have a valid archive once you download it... 'signatures' can also let you know you are receiving the archive from a valid source -- it depends upon the context