Briefing
On Unix-like systems a leading dot marks a file as hidden, so ls will not show it by default. Use ls -a to list *all* entries, then cat the one that looks suspicious.
Objective Find and read the hidden file in your home directory.
Stuck?
Take it one step at a time. Ask for a hint here, or type help in the terminal to
see the commands this challenge is about. Typing hint works there too.
That is every hint. If you are still stuck, run help in the terminal.