Answer Description

The act of observing a user enter confidential, security-related information while they are unaware is referred to as shoulder surfing.

Wikipedia

In computer security, shoulder surfing is a type of social engineering technique used to obtain information such as personal identification numbers (PINs), passwords and other confidential data by looking over the victim's shoulder. Unauthorized users watch the keystrokes inputted on a device or listen to sensitive information being spoken, which is also known as eavesdropping.