The use of the % symbol is to differentiate a System variable in a Batch file - %CD% would indicate that you should use the defined variable %CD% in a command wich returns the current CD drive letter
ie CD %CD% ...
would mean to change to the directory held in the variable %CD% - this may be a constant and the variable used to simplify the layout if the directory was a complex path or it could be a user supplied variable from the batch user