Seems to have been part of the user interface
https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Softw...
A set of interrupt-driven user interface routines called Pinball provided keyboard and
display services for the jobs and tasks running on the AGC. A rich set of user-accessible
routines were provided to let the operator (astronaut) display the contents of various
memory locations in octal or decimal in groups of 1, 2, or 3 registers at a time.
Monitor routines were provided so the operator could initiate a task to
periodically redisplay the contents of certain memory locations. Jobs could be
initiated. The Pinball routines performed the (very rough) equivalent of the
UNIX shell.
IIRC, pinball was also used for uplinks from the ground to the computer. From what I understand, such uplink commands simply consisted of a series of button presses to send to the computer, sent faster and more reliably than the astronauts could press the buttons themselves.