Newbie question : watermarking & filligrane

Hello,

I am using gallery 2 but I do not installed it. I am just a "simple & dummy user".

First of all, about the option "add filligran". I can use it foto per foto but it is not possible to add a filligran toa complete album. I am right ?

Second, something i do not uderstand well : what is the differe,nce between a filligran (a small picture added on a photo) and a watermark ?

Regards,