Hopefully, you understand how to use variables now. However, you might not yet grasp why we would want or need to use variables. It might just seem like extra work for a small payoff, right? Consider the next example:

reader@ubuntu:~/scripts/chapter_08$ vim name.sh 
reader@ubuntu:~/scripts/chapter_08$ cat name.sh 
#!/bin/bash

#####################################
# Author: Sebastiaan Tammer
# Version: v1.0.0
# Date: 2018-09-01
# Description: Script to show why we need variables.
# Usage: ./name.sh
#####################################

# Assign the name to a variable.
name="Sebastiaan"

# Print the story.
echo "There once was a guy named ${name}. ${name} enjoyed Linux and Bash so much that he wrote a book about it! ${name} really hopes everyone enjoys his book."

reader@ubuntu:~/scripts/chapter_08$ bash name.sh 
There once was a guy named Sebastiaan. Sebastiaan enjoyed Linux and Bash so much that he wrote a book about it! Sebastiaan really hopes everyone enjoys his book.
reader@ubuntu:~/scripts/chapter_08$

As you can see, we used the name variable not once, but three times. If we did not have the variable in place, and we needed to edit the name, we would need to search for every place in the text that the name was used.

Furthermore, if we made a spelling mistake in one of the places, writing Sebastian instead of Sebastiaan (which, if you're interested, happens a lot), both reading the text and editing it would take much more effort. Moreover, this was a simple example: often, variables are used many times (many more than three times at least).

Furthermore, variables are often used to store the state of a program. For a Bash script, you could imagine creating a temporary directory in which you'll perform some operations. We can store the location of this temporary directory in a variable, and anything we need to do in the temporary directory will make use of the variable to find the location. After the program finishes, the temporary directory should be cleaned up and the variable will no longer be needed. For every run of the program, the temporary directory will be named differently, so the content of the variable will be different, or variable, as well.

Another advantage of variables is that they have a name. Because of this, if we create a descriptive name, we can make the application easier to read and easier to use. We've determined that readability is always a must-have for shell scripting, and the use of properly named variables helps us with this.