Since the release of the original iPhone, Apple have produced phones with LCD displays, but with the impending release of the iPhone X, they have finally adopted OLED panels for their flagship phone. For fans of the iPhone, this is great news, as the display quality and brightness will improve drastically with these new OLED panels, in essence putting them on par with Samsung for display quality.
The down side of this however, is that due to the more complicated manufacturing process for OLED versus LCD screens, it looks like Apple will only produce half of their desired number of iPhone X handsets in 2017. As there desired number was 40 million iPhones, this means that Apple will be short 20 million phones by the end of the year.
So, if you're someone who picks up a new iPhone on release day, don't be surprised if there's none in stock for the first couple of months.