Need Help about PSD files

I have seen several times when I download files, that there are some files for repainting following in the package.
What do I do with these files they are in a format called PSD files ???
Are there any specific program needed to work with those files
help very much welcome
snoopy51
What do I do with these files they are in a format called PSD files ???
Are there any specific program needed to work with those files
help very much welcome
snoopy51
