In the world of photography, there’s no precise difference between wide-angle and ultra-wide angle. It’s kind of a judgement call. The general consensus is that for a 35mm image format — aka, “full-frame,” — the dividing line is 24mm. Anything focal length shorter than 24mm would usually be considered ultra wide-angle.
One most circa-2022 smartphones, the main camera is wide-angle. This is generally because a moderate wide-angle is usually the best lens to have, if you can only have one. So early on, smartphones had a single wide-angle camera. Once additional cameras were added, this main camera was certainly the best one, with the largest sensor. So going to a wider lens allowed for a shorter focal length and a larger sensor. Early smartphones might have a 30–40mm main camera focal length in full-frame terms, which is a moderate wide-angle. As sensors grew without getting fatter phones, this has moved to around 24–26mm on many smartphones.
The largest camera sensor on a phone in 2022 so far is that of the Sharp Aquos R6/R7, which sports a 1″ sensor, Sony’s new IMX989, the same size found in the Sony RX10 and RX100 compact digital cameras. In order to fit, this main camera sports a 19mm lens. Once camera and ultra-wide angle. But that’s needed to keep it short enough to ensure the phone has an acceptable thickness.
So what you’ll find is that the best camera in your phone is your wide-angle. If you have an ultra wide-angle camera, it will have a smaller sensors and a very small lens, somewhere around a 2mm focal length, with a full frame equivalence of 12–13mm. The lens is probably a partial fisheye lens, in which straight lines bend, to be straightened out by software.
The original ultra wide-angle cameras on smartphones didn’t even bother with autofocus, since a 2mm lens is going to have a hyperfocal focus range from maybe 1ft to infinity. But more recent phones are adding a focusing motor to these short lenses and, along with digital magnification (cropping), they’re using the ultra wide camera for a macro camera as well.