Search for and select the Standard edition ISO.
Note: The file name typically looks like: SW_DVD9_Win_Svr_Std_2016_64Bit_English_-2_MLF_X21-30317.ISO Download Windows Server 2016 Standard Iso Not Evaluation
If you're planning to use Windows Server 2016 Standard in a production environment, you need to download the full version, not the evaluation version. Search for and select the Standard edition ISO