Callback
A callback is a pointer to a piece of executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at some appropriate time.
Python Example
# Define a callback function. def sign(value): if value > 0: return 'positive' if value == 0: return 'zero' if value < 0: return 'negative' # Use the callback function. print(sign(5))