PHP mail function requirements

PHP mail function requirements

I am reading this from the PHP documentation:
Requirements For the Mail functions to be available, PHP must have access
to the sendmail binary on your system during compile time. If you use
another mail program, such as qmail or postfix, be sure to use the
appropriate sendmail wrappers that come with them. PHP will first look for
sendmail in your PATH, and then in the following:
/usr/bin:/usr/sbin:/usr/etc:/etc:/usr/ucblib:/usr/lib. It's highly
recommended to have sendmail available from your PATH. Also, the user that
compiled PHP must have permission to access the sendmail binary.
My question is what is this sendmail wrapper for POSTFIX that they are
talking about? Usually when I install POSTFIX with yum install the mail
function just starts sending mail? Is there something more to it than
that?
Thank in advance...