Make a secret folder on iPhone

There is no secret folder feature on iPhone. These are the closest options for photos, files and notes, and how private each one really is.

Build one from what Apple gives you

Photos. Hide them, and turn off Show Hidden Album if you want the collection out of sight.

Text. Lock a note, ideally with a custom password. Keep the title boring, since it stays visible.

Apps. Touch and hold, then tap Require Face ID, then Hide and Require Face ID. Apple notes that apps that come installed cannot be hidden.

PDFs. Add a password in Preview.

That gives you four locks and, usually, a single secret: your passcode.

Or use one place

A vault app gathers things in one spot. In Backroom you can add photos, videos, files and notes to a vault and open it with a pattern. Items stay encrypted on the phone, and there is no account.

Be honest about the word secret. Someone can see that a vault app is installed. Its icon can change on the paid plan, though the name under it stays Backroom. What the app protects is what is inside.