sessions...how to use not clear?

From what I understand about sessions you can give a session a particular name like doing: session_start("SessionName"); So in practicle means I can do this: <?php /*file #1*/ session_start($name); $_SESSION[name]=$name; $_SESSION[email]=$email; /*.....*/ ?> now my question is this: will i have to declare session_start($name); at the top of every file that needs to use that session name? or how does that work exactly (the docs didnt quite explain how to carry session names from file to file very well).. tnx