Memes

Each physical lens has a single focal length. "Wide" lenses have a wide field of view, and "telephoto" lenses can make very far away things look big in the screen. Have you ever tried to take a photo of the moon with your regular cell phone camera at default zoom? The moon itself is tiny, because the angular diameter of the moon from the surface of the earth is only about half of a degree (out of a 360 degree circle). So you need a very high focal length lens to be able to get the moon to fill up a photograph. Often, in sports, the sidelines have photographers with huge lenses trying to capture intricate detail (beads of sweat, texture of a ball) from 50-100 meters away.

You can stack multiple lenses in front of each other and vary the difference between them to "zoom" to different focal lengths. That versatility is great, and zoom lenses are very common on cameras. But because this feature requires the stacking of multiple lenses, the lens assembly as a whole will end up sticking out pretty far. Bad form factor for a phone.

So cell phones use a bunch of single-lens cameras to make the lens protrude less from the body of the phone, and use software to choose between the cameras: wide, medium, telephoto, or maybe even a super telephoto.

And once they had that in place, there were a few tricks that could be used where the software would evaluate 2 or more cameras simultaneously to try to capture more information with less blur to fill in more image detail than one camera could have, with that sensor hardware. So there are a bunch of computational photography tricks that make cell phone cameras look better with small, limited hardware.