A content delivery network, or content distribution network (CDN), is a geographically distributed network of proxy servers and their data centers. The goal is to provide high availability and performance by distributing the service spatially relative to end users. CDNs came into existence in the late 1990s as a means for alleviating the performance bottlenecks of the Internet even as the Internet was starting to become a mission-critical medium for people and enterprises.
In WordPress ecosystem the two most popular CDN are CloudFlare and BunnyCDN