About callback function

The puzzle said “In this puzzle, you will use a function that takes another function as an argument. The function being used as an argument is a callback function.”

I haven’t figure out which function was taken by the first function? Are “recordShow” and “setAlarm” functions"? Or callbackFunction(time,__) in line three is a function? (Sorry for my poor English)

Moreover, why there is no “return” in this code?

MyAssistant is a function and it has “recordTime” and “setAlarm” as an argument when the function is called. The “setAlarm” and “recordTime” are callback functions.