This is the package signature as generated by The GnuPG. This signature identifies the party that created the package. By verifying it you are sure that the package coming from a trustworty person or organization.
Here is the package signature:
-----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEABECAAYFAk9BUPQACgkQqesEzEdeXBFYxQCaAp0bGats6xbUx2xOhc77xL3s Q28AnRYtf2jUqfNwWpXMzEeVaLYGuT34 =197w -----END PGP SIGNATURE-----
You can save this signature in a text file (e.g. thunderbird-10.0.2bg-i686-1gds.txz.asc) in the same directory where the package file (thunderbird-10.0.2bg-i686-1gds.txz) resides and you can verify it by issuing the following command:
gpg --verify thunderbird-10.0.2bg-i686-1gds.txz.asc
NOTE: You need to import the public key of SlackPack first:
gpg --import KEY