The LaunchProcess plugin allows you to call external programs passing arguments from a recently uploaded file in CrushFTP. So you may want to process files using an external program after they were uploaded, or move them to another folder, etc. This plugin lets you configure this.
If you are on Windows, keep in mind many DOS commands you use are not actual programs but CMD.EXE commands. So to run a .bat file for example, you would need to do CMD.EXE with the arguments:/C;c:\myBatchProgram.bat;%the_file_path%;%user_name%
The semicolon separates the 'tokens' on the command line.