What specific lesson are you on? If you let us know where you're at in the course, we can review and clarify once we see what you're trying to understand.
The course is the System Administrator's Guide to Bash Scripting: Samples and Use cases: The input box
case "`cat choice.txt`" in
1) echo "Hello World"
2) echo "Goodbyeworld ";;
3) echo "Nothing";;
X) echo "exit";;
So, if there were no error messages sent to choice.txt, then please explain why we did this
case "`cat choice.txt`"