The use of App Security is simple: When you install the app, enter an unlock code in the form of a drawing. The first time that you enter this code is when it becomes the definitive code, and you’ll have to repeat it if you want to access the app. Once you enter the unlock code, you will be able to access the 'Secret photo gallery' folder or the 'Secret video folder' and once there, press the + sign to add those photos that you want to remove from the standard gallery and move to the secret gallery. The only way to see these photos will be through the secret gallery in the app, which you can edit when you want.
Another interesting feature that App Security offers is that it isn’t an app that appears in the apps menu, but rather is also hidden so that nobody knows that you are hiding images there, and if someone does access the app, they will still need to enter the same unlock code.
If you value your privacy and don’t want anybody to access your most private photos, App Security is what you need to protect your mobile’s audiovisual content.