Final answer:
The meaning of Com (mac) + "X" is concatenating the string "Com (mac)" with the string "X".
Step-by-step explanation:
In this context, "Com (mac)" refers to the command line interface on a Mac computer, which allows users to interact with the computer using text-based commands. The "+" symbol is used in programming languages, including Mac's command line interface, to concatenate or combine strings. So, "Com (mac) + "X"" means concatenating the string "Com (mac)" with the string "X".