One of today's leading display technologies, OLED stands for Organic Light-Emitting Diodes. It is a thin-film display technology in which organic compounds emit light – an optical and electrical phenomenon known as electroluminescence. Mostly used in mobile devices and wearables, OLED primarily competes with IPS screens when it comes to consumer electronics, and each technology has its pros and cons.
Note that similar technologies fall under the OLED umbrella: AMOLED and POLED. The difference between OLED and AMOLED is the latter's Active Matrix, which results in each pixel being independently activated. As for POLED, this technology employs a plastic substrate that allows for thinner and more flexible displays.
Current Samsung flagship phones are known for their AMOLED screens, which are produced by the company. Working toward advancing OLED technology, Samsung has integrated the touch function into the screen of some of its products, marketing their displays as Super AMOLED. Although the South Korean multinational wasn't the first brand to release a smartphone with an AMOLED display, Samsung is currently the largest producer of AMOLED screens for a wide range of devices (phones, tablets, TVs), along with LG, known for POLED screens.
The main advantages of OLED in comparison with IPS displays are increased power efficiency, deeper blacks, and more vibrant colors, all of which result from individual pixels being switched off. As for disadvantages, OLED is more expensive than IPS, and issues like screen burn-in and color shifts (due to organic compound degradation) may happen, which would decrease an OLED display's lifespan.