[john2k]

The main goal with CDNs, the way I understand it, is to reduce network latency by reducing the distance between the end user and the content.

CDNs reduce the distance over the wires that the data needs to travel, reduces the number of network hops and helps to avoid your data needing to traverse over congested network equipment (or the chance that it might hit congested equipment on the networks that are skipped).

Reducing latency is very helpful for videos and especially streaming media, which many of the CDN networks like to focus on (more bandwidth income for them with video).

Cloud hosting is defined differently by many hosts. The inconsistency makes it a bit difficult to compare. Not all clouds are the same and not all clouds are also content delivery networks.