How is Windows Server OS different from the regular Windows 10 Home/Pro OS?

I’m currently looking into using SAP B.One for my company and I’ve been told that we will need Windows Sever OS for the server and we will need to buy a certain number of CAL and RDS for the domain and remote users. All my user PCs have Windows 10 OS installed on them. Should I need to purchase further licenses as well? What will be the purpose? https://trackeasy.fun/usps/