confirm order error

q1) Once you have all the details from the user on a payment, then I get an email error on confirm order (the email is a valid 1). Do I need to configure this to an actual paypal/sandbox account ?

If you are going to use paypal then yes, but sandbox not good idea for testing,
so test by entering product for say $1.00, you can always refund via paypal
account.

I though sandbox for developed for testing, I am confused.

I don't really know enough about how paypal works to be honest.

I though sandbox for developed for testing,It is but does not work well when testing paypal payments
in zencart

I am confused about paypal. The account I have and instructions say you paste paypal buttons on your site. It then horribly takes you to their website for further forms.
Now with zencart all the forms are done onsite then asks paypaly for confirmation which i prefer, but don't understand how it works.

Where can i get more information on the logic/setup because I have no idea about paypal. I am finding it hard to get information on it oddly enough.