Learn HTML by Building a Cat Photo App - Step 55

Hi @masoud.fathi and welcome!

Dont worry, you are doing great. Take your time to understand the concepts.
Here you can check a couple of answers about this step:
Step 12
An even check input element in w3schools or mdn web docs.
Also on freeCodeCamps news you can find some good videos or posts. For example:

# Learn HTML – Responsive Web Design Study Guide post
Learn HTML – Beginner’s Course Great video!!

Happy coding, I hope that helps