What are the main functions of client operating system, and how does it differ from a server operating system?

The OS that operates within the desktop or various devices which obtain services from a server. It is mainly used for personal use computers and the OSs are Microsoft, Mac.
But the server OS is used on servers, and it is mainly used in big organisations or enterprises, and the OSs are windows server, Redhat, Linux

What is scale up and scale down?

What is vertical scaling?

which is permanent memory? EBS volume or Instance store?

what is Instance store?