Much of our digital world depends on a little technique discovered out of necessity in the early days of computing. This paradigm of how digital devices communicate and co-operate, makes the entirety of the internet possible and efficient. So to understand information technology and online content delivery methods, you must understand what client-server architecture is.
Look up Content Delivery in all the standard informative places and they will talk about the delivery of media content, and about the almost equivalent and mostly overlapping field of content distribution. All quite dry and academic, really, but I think almost everyone today needs to have a deeper and more intimate understanding of the tasks, issues, tools and challenges of content delivery, because increasingly we are all part of its wide scope.