Content delivery networks (CDNs) serve static assets via globally distributed servers to improve web app loading speed.
The 5 hour CDN explains the basics of what CDNs are and how they are a combination of many standard web server components, but used globally and at scale.
MaxCDN vs CloudFlare vs Amazon CloudFront vs Akamai Edge vs Fastly compares and contrasts the most popular CDN services based on features, performance and pricing. Note that Full Stack Python uses Cloudflare to serve all content.
Do not let your CDN betray you: Use Subresource Integrity describes the security implications for CDNs with unexpectedly modified content and how Subresource Integrity in modern web browsers can mitigate this vulnerability if used properly.