SaaS is hand off to some magical thing that handles everything for you. Managed services in clouds offer many different levels of how much they manage for you.

SaaS is hand off to some magical thing that handles everything for you. Managed services in clouds offer many different levels of how much they manage for you. IaaS just frees you from having to buy, install, and maintain your own servers, disks, network cabling, HVAC units, physical security, land, dedicated fiber lines from the local ISP, but you still get all the same complexity in terms of setting up all of these things to run your application. What level of detail you have to worry about is entirely up to you. Use nothing but fully managed application services and everything will be easy. Turning "buy a new server and attach it to the various networks it needs access to" into button clicks is still making at least a few things much easier.