For starters, CDN is a “network of servers” type of technology which has been around longer than cloud computing in its current form. Cloud computing is about delivery of different services through the internet, involving tools and applications, such as data storage, servers, databases, and software. Cloud computing helps divide a large computing resource, such as processing power, into smaller pieces which you use remotely.
Cloud computing refers to a big group of servers, “situated” in one data center building, usually at one location. Whereas CDN is also a group of servers, but distributed around various locations, thus ensuring your visitors with a better and faster access to your site.