Question

Hello..I wanted to ask what PEAR is.  Please excuse my ignorance...
I just took over managing a friends website, & I am not to familiar with
PHP.  
I am going through his file structure, & noticed a folder called  _pear.
Inside there is a file called PEAR.php & a folder called Image.
I'm trying to figure out if & where the website is utilizing this, & if so,
what for.  

I appreciate any help or insight you may have.
Thank you!!!

-JG