Final answer:
Holding down "Ctrl + Shift + Esc" launches the Task Manager, used to manage running programs and processes.
Step-by-step explanation:
When the technician instructs a user to hold down "Ctrl + Shift + Esc", they are launching the Task Manager. This utility is used to view and manage the programs and processes currently running on a computer. If a program has stopped responding, it can often be found and closed through the Task Manager, which can help restore normal operation to the mouse and other system features.