Windows Server has historically been licensed by physical processors-sockets, but Windows Server 2016 Data Center and Standard depart from socket-based licensing and into processor-core base licensing. The base Windows Server 2016 Data Center or Standard come with 16-core license. 
Additional licenses to cover larger core-count processors are available in increments of 2-core and 16-core additional licenses for respective editions. All cores have to be licensed for a valid shipping configuration. 

This Excel-based calculator have been created to aid Customers in selecting appropriate additional Windows Server Licensing with their Dell EMC PowerEdge Servers