The screen, when combined with the touch element, is 'the' major element of the user interface and as such we go to great lengths when testing screens during our review process to measure a displays quality by measuring Contrast Ratio, Color Calibration, Brightness and Sunlight Legibility.
LCD (Liquid Crystal Display) displays consist of a matrix of Liquid Crystals. Liquid Crystals do not emit light themselves and are reliant on some form of back-light to illuminate the whole display. As a result LCD displays can be very visible in direct sunlight.
Our tests show the IPS-LCD matrix in detail for the iPhone 8 Plus
IPS-LCDs provide a superior viewing angle and better color reproduction than non IPS-LCDs due to the layout of the LCD's themselves. This has become a common display type for mid-range to high-end phones.
OLED & AMOLED utilizes 'organic' LEDs which emits light and in the majority of cases does away with the need for the back-light of an LCD display resulting in a potentially thinner panel.
It provides less washed out 'blacks' with a better contrast ration and is highly visible in low light conditions.
When magnified, the differences between panel types are clear
They consume less power as opposed to LCDs which always have the back-light on. When a pixel is 'black' on a OLED/AMOLED display the pixel is truly off.