Several of your computer files are "for your eyes only". If you want to be sure that other people cannot read your letters or see your photos, you should encrypt them and protect them with a password. There are several software programs that can do this for you.
Windows Explorer has its limitations. That's why there are now several programs that can be used to do the same tasks (and more), but easier and better. My favorite file management software Total Commander.
You use passwords to protect something. it’s like using a key to lock your house. To be safe it is important to use strong passwords. Find out how, and read also my page on password strength.