Good smartphone security practices are essential. Check Settings > Device > Private mode to see the specific solutions Samsung has built here.
For example, if you turn on private mode you can jump into the gallery, select a batch of photos, and make them private. Only you can see them by enetering a password, pattern, or fingerprint.
These privacy features only work with Samsung's apps, like Gallery, Video, Music, Voice Recorder, My Files, and S Note. However, it's useful if there are certain notes, videos, or images you don't want the world to know about if you need to let someone briefly use your phone.