: This indicates it is the 15th piece of a larger file that was split into multiple parts using WinRAR or a similar compression tool.
To use this file, you would generally need to have (part01, part02, etc.) in the same folder and then extract them to reconstruct the full video file. Amst3rd4m.4K.yamil.part15.rar
: The subject is a 4K resolution video of Amsterdam (using "leetspeak" or obfuscation for the name). : This indicates it is the 15th piece