Checkout Terms and Conditions
This screen allows you to add specific terms and conditions to the end of your checkout process. These appear as checkboxes that the customer must tick for checkout to proceed.
To use these you have to create at least one entry on this screen and then activate Terms and Conditions in System > Checkout > Checkout Options > Enable Terms and Conditions
Update You can edit these terms and conditions under Sales > Terms & Conditions
UPDATE 2 PayPal Terms and Conditions Tutorial can be found here: http://www.magentocommerce.com/knowledge-base/entry/setting-up-billing-agreements-through-paypal