You're probably already aware that since you are checking out through PayPal all information being transmitted is made secure by them.
But this notice is to explain that any potentially sensitive information gathered inside the Immortal Ephemera Store is also secure:
The Immortal Ephemera Store is runs through a platform called Ecwid.
The Ecwid shop containing all of Immortal Ephemera's products is embedded into the pages of this website.
Here's how Eugene of the Ecwid Team explains Ecwid's security:
When you use Ecwid, all the sensitive information is transmitted via HTTPS protocol during checkout. So you don't need to install SSL certificate or change anything -- Ecwid checkout is already secure.
You will notice this most prominently during checkout, specifically when you reach the page asking for your credit card information. Scroll to the bottom of that page and look at the bottom right corner of the checkout form (not the Immortal Page, but the area inside the page asking for your information).
You'll see a yellow padlock denoting that the page is secure. Hover over it and you will see further details: