Why And Which CDN Should Be Used For WordPress Website ?
Why ? if you are not using a CDN then your site will be served via your main server to visitors, but if you are using a CDN your site will be served via nearest server to the visitors which are browsing your website, because a CDN provider has many servers around the world which allows it to serve your site blazingly faster than your main server.
Which ? if you can pay for CDN service then use MaxCDN but if you are looking for a free CDN CloudFlare is the best choice, cloudflare free CDN services are limited but they’ll surely boost your site performance.