Q. What licenses are required to run container instances?
A. Windows Server 2016 introduces containers which offer a very lightweight to quickly spin up instances of services while still offering isolation and resource control. There are two types of containers, Windows Containers and Hyper-V Containers and I explore the differences at http://windowsitpro.com/windows-server-2016/differences-between-windows-containers-and-hyper-v-containers-windows-server-201.
The type of container impacts the licensing requirements as documented at https://www.microsoft.com/en-us/Licensing/product-licensing/windows-server-2016.aspx.
If you use Windows Containers then you can run an unlimited number of containers on Standard or Datacenter.
If you use Hyper-V Containers then you can run an unlimited number on Datacenter but 2 on Standard (since a Hyper-V container is essentially an automatically managed VM with a separate OS instance running Windows Server).