GnuPG is a command line tool without any graphical user interface.
It is an universal crypto engine which can be used directly from
a command line prompt, from shell scripts, or from other programs.
Therefore GnuPG is often used as the actual crypto backend of other
Full OpenPGP implementation (see RFC4880 at RFC Editor).
Full CMS/X.509 (S/MIME) implementation.
Runs on all Unix platforms, Windows and macOS.
A full replacement of PGP; written from scratch.
Does not use any patented algorithms.
Freely available under the GPL;
Can be used as a filter program.
Better functionality than PGP with state of the art security features.
Decrypts and verifies PGP 5, 6 and 7 messages.
Supports RSA, ECDH, ECDSA, EdDSA, Elgamal, DSA, AES, Camellia,
3DES, Twofish, SHA2, and many more algorithms.
Language support for a load of languages.
Online help system.
Optional anonymous message receivers.
Integrated support for HKP keyservers (sks-keyservers.net).
and many more things….