If you are running a script on your localhost development windows box you may need to make a few changes to your php.ini file to actually send the mail. If so, open the ini file and find instance of smtp and/or mail.
The php docs also suggest looking into PEAR MAIL if you are up to that level.
The mail() function is quite straightforward and you can, for instance, create an input form that then inserts the to/from/subject/body values in varibles upon submission that then get plugged into the mail() function.
How do i send email with php
Is there some computer configuration needed too for this purpose