Cloudflare is a service (or a CDN, Content Delivery Network) that deals with the security and performance features (among other things) of a wide network of websites. It acts as a reverse proxy, a middleman between you—the user—and a given website. When you go visit that site, you’ll be directed to one of the Cloudflare’s servers instead of the actual site’s servers.
This allows Cloudflare to ensure you’re a legitimate user (thus protecting against denial of service attacks), load the site faster (since they’ve cached certain parts of the site), and protect against downtime (since they have multiple servers worldwide and can fall back on any server if one has a problem).

Cloudflare safeguards DDoS attackers don’t get their traffic through to the actual website.
In short

Kiran KumariPosted Apr 18, 2019, 2:01 PM
Very knowledgeable article