PEAR is short for "PHP Extension and Application Repository" and is pronounced just like the fruit. The purpose of PEAR is to provide:
A structured library of open-source code for PHP users
A system for code distribution and package maintenance
A standard style for code written in PHP, specified here
The PHP Extension Community Library (PECL), see more below
A web site, mailing lists and download mirrors to support the PHP/PEAR community
PEAR is a community-driven project governed by its developers. PEAR's governing bodies are subdivided into the PEAR Group, Collectives, and a President. PEAR's constitution (adopted in March 2007) defining these groups is documented here. The PEAR project was founded in 1999 by Stig S. Bakken and quite a lot of people have joined the project.