I'm writing a tell-a-friend script. A user can send the URL of the page he/she is on to a friend. They will fill out a form with their email and then their friend's email and send it. What would the code be that would send the url??

Also how do I set up the so that it will send the email I have no idea how to do this...

PHP Code:
"From: $first_name $last_name",
"To: $to",
"Subject: Check out this site!" 
I can do this much but how can I get it to actually send the email and appear from the address of the user ect. Do I need to use SMTP (I have no idea what that is)

Anyway you can see I'm lost any guidence would be great!