PHP on Pear

Hello, I've been programming on PHP for almost a year now, many examples that I've gone through or some of the reference books that I've read and many websites which show examples of PHP pgramming seem to be using PEAR package, and I've never used PEAR or any other Package, I was wondering whats the advantage of using PEAR instead of the using PHP directly in the code or maybe even creating our own functions in PHP. I am really confused about this now, earlier I used to neglect these things, but now I curious and getting a little impatient coz I am starting some work on a project for myself, and I would want to keep changing the code all the time. Can someone guide me on this please? Thanks, Vinay Kannan.