This is the first CU for the new SharePoint 2016 Server!
see here the KB 2920721 – SharePoint Server 2016 April 2016 CU
After installing the CU, we still need to run the SharePoint 2016 Products Configuration Wizard.
If you want to use the commandline with psconfig.exe please read first "Why I prefer PSCONFIGUI.EXE over PSCONFIG.EXE"
Other SharePoint Builds and version tables: