A function is some amount of code you can reuse in your program. You create a function using a function definition which names the function and has its code. A function call is when you use a function by its name somewhere in your program.
A function definition is a block that has the name of the function and its code.
function doSomething() {
}
A function call is when you want to use the code in the function at some place in your program.
function doSomething() {
}
doSomething();