The Add to cart popup modal appears on the home, shop, product, product category, and the custom page once the customer clicks on the add to cart button. The popup modal asks guest users to enter their email with their consent.

The email field in the ATC popup can be set as optional that means the popup to ask for an email address will be displayed, but the customer can simply click on the "No thanks" link & proceed to add the item to the cart. You can learn more about the Add to cart popup modal here.