“plot_Escan_H125_N3LO.C” is the macro and “plot_Escan_H125.pdf” is the plot of one of the XS-plot for the YR-n4. 

Inside it calls LHCHiggsXXX .c files (.c_file1, .c_file2, c_file3, .c_file4) and .h files (.h_file1, .h_file2) and then adds some additional instructions.  

A “basic example” is also given (LHCHiggsExample.C) macro.