The iPhone XS and iPhone XS Max (stylized and marketed as iPhone Xs and iPhone Xs Max; Roman numeral “X” pronounced “ten”) are smartphones designed, developed and marketed by Apple Inc. They are the twelfth-generation flagships of the iPhone, succeeding the iPhone X. Apple CEO Tim Cook announced the devices alongside a lower-end model, the iPhone XR, on September 12, 2018, at the Steve Jobs Theater at Apple Park. Pre-orders began on September 14, 2018, and the devices went on sale on September 21.

Improvements besides increased computing speeds include dual-SIM support, filming with stereo audio, and strengthened water resistance.

Excerpt source – Wikipedia