Notch

A "notch" refers to a physical area reserved for sensor(s) on the display of a device, usually at the top. This has become a design element of since 2017, balancing the need for front-facing cameras, microphones, and/or other sensors with consumer demand for larger edge-to-edge screens.

Background
The (PH-1), announced in May 2017 and released in August, was the first mobile device to implement a "waterdrop" style notch to mixed reviews. Then Apple's introduction of the wide notch on the iPhone X, announced in September 2017 and released in November, popularized the design. Android phone manufacturers implemented various approaches, ranging from a "holepunch" style to a mechanical pop-up or slider to hide the front-facing camera and sensors when not in use.

Hiding the notch
3rd-party developers have created software to obscure the "notch" in iOS and macOS by blacking out the horizontal area around it.

Under-display camera technology
In 2020, became the first company to ship a smartphone with a camera hidden under the display with their Axon 20 5G, followed in 2021 by Samsung with their. This is made possible by reducing the resolution of the display area in front of the camera, while also compromising the apparent resolution of the camera itself. Though the quality of subsequent under-display camera setups are improving, a key technical challenge is that this can only be accomplished with an OLED display which acts as a "screen door" in front of the camera that tightens as the display resolution is increased in newer models. Microsoft is presently researching under-display camera technology for the purpose of being able make direct eye content between video callers.