GnuPG key capabilities

[Joe Vender]

> >A specific key's capabilitie(s) are the defined purpose(s) or usage of
the
> >particular key. For example, when you generate a key, you are asked
what
> >the key should be used for (encrypt only, sign only, encrypt & sign,
> >authentication, certification). These are the possible key
capabilities,
> >and when chosen at key generation time, become the key's
capabilitie(s).
> >The key's capabilities are displayed after "usage:" when you do an
> >gpg --edit-key.
> >
> Ah,.. thanks :-)
>
> Ok,.. encrypt/sign is clear,... but what can I do with authentication an
> certification?

See:
http://lists.gnupg.org/pipermail/gnupg-users/2005-April/025390.html