Mechanicals = Files prepared for print
Words and graphics ...
The most important step in successful production is communicating with the printer who will be executing the job. Here you'll see instructions to the printer; but verbal communication can be even more important. I learned about production and prepress through dialogue with each printer who was producing my designs.
Clear communication is key to any successful collaboration.
FYI, Centara Global was never my employer, but I recreated their designs to illustrate how a certain product would be sent to the printer. You can see why one might not understand from a verbal explanation alone. Words + graphics