Like PGP, GPGTools encrypts and digitally signs your data before sending it over the Internet, if you know how public/private encryption key works it will only take you a couple of minutes to master GPGTools, it provides you with a nice front end for GnuPG and bells and whistles like the Enigmail plugin. You will need to understand the concepts behind digital signatures and public/private encryption keys before using it, a well worth time investment for anyone who cares about computer privacy and security.
You don’t have to use Thunderbird for encrypting emails, Apple Mail works with GPGMail to decrypt and encrypt messages, which one you use is up to you. GPGKey Chain Access lets you store and edit encryption keys, essential to create key pairs, GPGTools is very similar to GPG4Win, another open source OpenPGP implementation for Windows users only.
The expensive business focused PGP software sold by Symantec includes full disk encryption and secure data wiping, home users can get all of those features without spending a dime by using three different tools, GPGTools to encrypt/decrypt email, Truecrypt to fully encrypt your Mac computer hard disk and EdenWaith Permanent Eraser to securely shred your private files.