The first launch models of PSVita uses OLED displays made by Samsung, called Super AMOLED Plus. AMOLED stands for Active-Matrix Organic Light-Emitting Diode, and Super AMOLED means it uses an evaporating touch screen layer directly on top of the OLED layers (instead of leaving a gap between the touch screen layer and the OLED). The Plus behind Super AMOLED is important, as it signifies the arrangement of the subpixels are normal RGB. Luckily the PSVita uses this Super-AMOLED Plus technology, which basically match the number of Red and Blue subpixels with the number of Green pixels (essentially regular RGB). The PSVita is very close to the iPhone 4 in resolution (just 96 fewer horizontal lines).
Samsung also makes a lower quality OLED called just Super AMOLED (without the Plus), which uses PenTile Matrix subpixel arrangement. Pentile Matrix uses subpixels to trick your eyes into seeing more resolution. For example, ClearType (a Microsoft technology) uses subpixels to smooth font displays. When a LCD monitor specifies that the resolution is 1024x768, then that means the monitor can display that many pixels (horizontal and vertical) all at once in different differentiated colors.