There are several ways to protect your Android phone from the gaze of others, either through a password, fingerprint access or even hiding your apps; however, many times it is not very practical if you have to lend your phone to someone and you cannot watch what content they are going to access. That's why it is possible to activate the "guest mode" for more privacy in certain moments.
WhatsApp: ¿Cómo activar el modo 'Halloween'? Así puedes cambiar el ícono por una calabaza