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))