Setting up store with PayPal

I’m trying to set up a store with PayPal. After watching the video demos on the site, I don’t have these two questions answered:

[LIST=1]
[]Does PayPal Pro cost more than Standard to use? The video said “no fees” for both of them, but clearly Pro is better because it allows you to set up the cart directly on your website. So what’s the catch?
[
]How does PayPal know what items a buyer has in the cart?
[/LIST]