maybe don’t just assume all of us knows what ‘GPR’ is. For those maybe wondering, it stands for “General Purpose Registers”.
That is stated in lesson 1. It’s in the first sentence that mentions “GPR” and in the heading directly above it.
(By the way, I’m not the author.)
And when Cloudflare is the proxy for a web site, it’s Cloudflare that provides the HTTPS connection, meaning that you don’t actually have an encrypted channel directly to the site. Cloudflare is the man-in-the-middle eavesdropping on all of your communications with that site. Your bank transactions, your medical records, your personal messages, etc.