Explain like I only speak in plain English

A function can be thought of as a machine that performs a specific task. Such as make sandwich. Every time you want a sandwich to be made, you just have to turn on the machine. Or execute the function, as programmers would say.

Functions are important in programming because it allows programmers to dissect parts of the program where the same task is carried out repeatedly.

Instead of repeating all the instructions to make a sandwich. The programmer can pack all the instructions inside a function, call it makeSandwich. And execute the function whenever a sandwich needs to be made.

Explain like I'm a total nerd

Functions can take inputs, and give outputs. You can think of the inputs as ingredients. Outputs as the end products. For a function that is to make sandwiches. You can give it inputs of bread, peanut butter, and jelly. The output would be a peanut butter jelly sandwich.

The coolest thing about functions is that they can contain and use other functions too. As an example, our makeSandwich function can use the toastBread function to toast the bread before making it into a sandwich.

Explain like I Like Examples

The following is a simple function written in JavaScript. It will add the two input numbers and return their sum.

var sum = function (a, b) {
  return a + b;
}
// sum(3, 7) will return 10

Explain like I like videos

Explain like I already know it

Functions are important as it helps keep our programs DRY (Don't Repeat Yourself). Whenever you find yourself repeating identical or similar code, you should consider abstracting it into a function.

Another neat thing about functions is that they can call themselves, these are called recursive functions. Programmers often rejoice whenever they see an elegant recursive function in use.

Programming

Programming is creating instructions for the computer to perform specific tasks. A person who writes programs is called a programmer. There are many different programming languages a programmer can write programs in.

Variable

A variable is a temporary storage unit in a program. You can think of it as a box. You can use this box to hold an item. You can retrieve the item stored, or swap it with another item.

Conditional

A conditional represents a choice in a program, it dictates what happens next. Such as, if today is a Monday, then make a reservation for dinner with the family, otherwise, eat dinner alone with TV.

Loop

Loop is a program that repeats a set of instructions until it is asked to stop. As an example, we can write a loop program to print out "Hello" 3 times. Loop is a fundamental concept in programming.

Foo Bar Baz

Foo, Bar, and Baz are used as placeholders when giving examples in programming. It's like placeholder names that refer to objects or people when telling a story. Such as widget or "John Doe". The actual names are irrelevant and do not affect the message being conveyed.