Why do I see so many comments in this format?

Answer 1

Those are phpDocumentor comments. Comments starting with /** are used by documentation generators (by convention) to create documentation for the project. Here is a quick start guide for phpDocumentor.

Answer 2

Many documentation generators can read from formats like this.

This is also used by many IDE's to help with coding. (for example Zend Studio and others)

/**
 * Title
 * 
 * @author Me
 * @copyright 2009
 * @name test
 * 
 * @param int $foo
 * @return bool 
 */
function test($foo)
{
 return is_int($foo);
}