What is the Job of second lens in dual camera Mobile phones

Question

Somewhere I read that two lenses are required to create a DSLR effect- Blurring the background. But today I read, the Aperture size is responsible for blurring the background,

So any lens (single camera) with a large aperture will blur the background, so No need to add another one.

In my iPhone X, there are two lenses- wide angle and telephoto lens, so does that mean wide is used for closer objects and telephoto is used for distant objects. ??

Or

Two lenses are required to create a sort of 3d effects in portrait pictures?

Answer 1

On small focal lenses (and the small sensor size of the phone requires small focal lengths), there is a very wide depth of field, so you don't get any significant background blur.

The second lens has a different perspective from the main one, and software can deduce the distance of objects from their difference between the two images, from which you can synthesize a pretend focus blur.