[function] How to explain callbacks in plain english? How are they different from calling one function from another function?

There's two points to explain, one is how a callback works (passing around a function that can be called without any knowledge of its context), the other what it's used for (handling events asynchronously).

The analogy of waiting for a parcel to arrive that has been used by other answers is a good one to explain both. In a computer program, you would tell the computer to expect a parcel. Ordinarily, it would now sit there and wait (and do nothing else) until the parcel arrives, possibly indefinitely if it never arrives. To humans, this sounds silly, but without further measures, this is totally natural to a computer.

Now the callback would be the bell at your front door. You provide the parcel service with a way to notify you of the parcel's arrival without them having to know where (even if) you are in the house, or how the bell works. (For instance, some "bells" actually dispatch a phone call.) Because you provided a "callback function" that can be "called" at any time, out of context, you can now stop sitting at the front porch and "handle the event" (of parcel arrival) whenever it's time.

Examples related to function

$http.get(...).success is not a function Function to calculate R2 (R-squared) in R How to Call a Function inside a Render in React/Jsx How does Python return multiple values from a function? Default optional parameter in Swift function How to have multiple conditions for one if statement in python Uncaught TypeError: .indexOf is not a function Proper use of const for defining functions in JavaScript Run php function on button click includes() not working in all browsers

Examples related to callback

When to use React setState callback How to send an HTTP request with a header parameter? javascript function wait until another function to finish What is the purpose of willSet and didSet in Swift? How to refactor Node.js code that uses fs.readFileSync() into using fs.readFile()? Aren't promises just callbacks? How do I convert an existing callback API to promises? How to access the correct `this` inside a callback? nodeJs callbacks simple example Callback after all asynchronous forEach callbacks are completed

Examples related to language-agnostic

IOException: The process cannot access the file 'file path' because it is being used by another process Peak signal detection in realtime timeseries data Match linebreaks - \n or \r\n? Simple way to understand Encapsulation and Abstraction How can I pair socks from a pile efficiently? How do I determine whether my calculation of pi is accurate? What is ADT? (Abstract Data Type) How to explain callbacks in plain english? How are they different from calling one function from another function? Ukkonen's suffix tree algorithm in plain English Private vs Protected - Visibility Good-Practice Concern

Examples related to terminology

The differences between initialize, define, declare a variable What is the difference between a web API and a web service? What does "opt" mean (as in the "opt" directory)? Is it an abbreviation? What's the name for hyphen-separated case? What is Bit Masking? What is ADT? (Abstract Data Type) What exactly are iterator, iterable, and iteration? What is a web service endpoint? What is the difference between Cloud, Grid and Cluster? How to explain callbacks in plain english? How are they different from calling one function from another function?