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 command gpg from GnuPG 1.x, which might be better suited for server and embedded platforms, the 2.x version is commonly installed under the name gpg2 and targeted to the desktop as it requires several other modules to be installed.
See Option Index, for an index to gpg2's commands and options.