2 Answers
It was created in your EC2 instance and in the directory you were present. In video, txt file was in root home.
You create this file using echo "Hello" > hello.txt. This is a basic linux redirect, taking the output of the echo command, and directing it into a new file called hello.txt.
This get’s created in whatever directory you are located in while running this command. If you were experimenting with jumping around the instance (cd) you could have lost track of where it is.
Hope this helps!