User adding extra form boxes

Hello,

I'm not sure what the exact parlance is here but can anyone advise me on how about doing the following?

Like on many Airline websites the user can click a button to 'add another passager' or whatever and a new form box/form boxes pop-up underneath. I'm trying to do the same thing (but with adding food to a list) but also wondering the recommended way to do it.

I was thinking a bit of Javascript activated on click, to draw up a new form box in the form with a different ID/name to be posted through to the update page along with everything else. I'm still learning javascript - does anyone know a good tutorial for this? I would search myself but I'm not sure what this would come under.

Thanks

Chris