There are actually two public keys?

[Robert J. Hansen]

Lucio Capuani wrote:
> Nevertheless, the fact that GPG uses "two keys", I mean a main key and a
> subkey, confuses me. Are those "two keys" the private/public pair? Or
> it's else?

There are two keypairs.  One keypair is used for signing, and the other
is used for encrypting.  The private part of the signing keypair is used
 to generate signatures; the public part is used to verify them.
Likewise, the private part of the encryption keypair is used to decrypt
documents; the public part is used to encrypt them.