Defining functions

We can define a function in three possible ways:

1) With parentheses

usage() {
    echo "Use it!"
}

2) With the keyword function

function usage {
    echo "Use it!"
}

3) With parentheses and the keyword function

It is redundant, so it is not really used that much, but you can define a function like so:

function usage() {
    echo "Use it!"
}