Cloudflare Full Strict HTTPS flow

I would like to understand Cloudflare full(strict) SSL flow. Because if user type it redirects to Cloudflare web servers. So how Cloudflare decrypt HTTPS data before sending to origin host without browser warning ? How Cloudflare match certificate data between Browser and Cloudflare servers. Because main certificates situated on origin web server and only Original web server can decrypt after get HTTPS data.