gpg2 is the OpenPGP part of the GNU Privacy Guard (GnuPG). It is a tool to provide digital encryption and signing services using the OpenPGP standard. gpg2 features complete key management and all bells and whistles you can expect from a decent OpenPGP implementation.
In contrast to the standalone version gpg, which is more suited for server and embedded platforms, this version is commonly installed under the name gpg2 and more targeted to the desktop as it requires several other modules to be installed. The standalone version will be kept maintained and it is possible to install both versions on the same system. If you need to use different configuration files, you should make use of something like gpg.conf-2 instead of just gpg.conf.
Documentation for the old standard gpg is available as a man page and at see GnuPG 1.
See Option Index, for an index to gpg2's commands and options.