Organic and Inorganic light-emitting diode (LED) based television offers unrivaled contrast.  They provide a more dynamic grayscale and broader color volume than LCD television.  The source of light-emitting diode technology lies in the oldest of solid-state technologies, the diode.

OLED & IOLED descend from the pioneer of solid-state electronic technology - the diode.  An early example is the 1906 crystal radio.  It used a diode crystal called a 'cat's whisker' to detect electromagnetic radio waves (continuous electric sparks), induce an electric-magnetic current, and modulate a crystal earphone that created audible radio.  This 'old diode' consisted of mineral crystals such as galena -- lead crystal.

Another characteristic of the diode, it passes electric current in one direction while blocking electric current in the opposite direction.  This one-way behavior is called rectification. This trait demonstrated by the rectifier converts alternating current to direct current in the electrical product throughout our homes.

Diodes regulate voltage, protect circuits from surges, detect and generate radio waves, plus produce light.  Diodes perform these functions by varying their materials and using a technique of adding impurities called doping.  The diode materials include organic carbon-based silicon and inorganic substances such as germanium. 

Light from a diode, derived from the phenomenon of 'electroluminescence', is an electrical phenomenon in which a material emits light in response to the passage of an electric current.  Diodes that produce light are the basis of OLED and IOLED TV.

An OLED and IOLED television screen is a solid-state electronic device.  They consist of an electroluminescent layered cell plate or film situated between anode and cathode electrodes.  The electrodes are a transparent front anode overlay and a rear metallic cathode layer.  The anode/cathode layers sandwich the electroluminescent cell. 

Injected positive and negative electric charges recombine in the emissive layer to produce electroluminescent light.  The brightness and color are enhanced by 'doping' the emissive layer with a small amount of highly fluorescent molecules.  The result offers a lower black level and a wider grayscale with more accurate broader color volume than LCD TV.

IOLED screens are inorganic semiconducting crystal wafers made of gallium arsenide or gallium nitride.  OLED screens are organic crystal wafers made of materials such as plastic or glass. Due to lower thermal conductivity, an OLED emits less light than IOLED.  IOLED also has a longer illuminating life than OLED.  Yet OLED screens still have a life expectancy that is similar to plasma and LCD technologies. The key difference is cost.  OLED is less expensive to produce than IOLED.

Manufacturers will attempt to differentiate their LED based TVs from their competitors.  Therefore, prepare for an advertising avalanche of video 'buzz words'. 
Here is a shortlist of what you may confront.

Active Matrix OLED or AMOLED uses a thin-film transistor (TFT) backplane to control each sub-pixel of the display -- on/off or more/less light.
All OLED and IOLED televisions are active-matrix technology.

WOLED (Super AMOLED) adds a fourth white sub-pixel.  The extra white sub-pixel increases brightness.  Each sub-pixel generates white light via a stack of red, green, and blue OLEDs.  Each stack engages a red, green, or blue filter except for the fourth white sub-pixel. 

OLED Options

LG OLED TV panels are WOLED.
OLED TV descriptions do not typically include the "W" in WOLED.
LG, the lead manufacturer of WOLED panels, offers many panel options.
This includes 4th Gen OLED,  Micro Lens Array, OLED EX, OLED 120 Hz, & OLED 60 Hz.
Most OLED TV brands use LG OLED panels.

4th Generation Primary RGB Tandem Structure OLED

The 4th generation LG panel sandwiches their red and green panels between two blue layers, for a total of four layers.
Narrow-wavelength blue LED light produces less brightness than red and green LEDs.
The extra blue layer increases brightness and eliminates the need for micro lens array lenses.

LG OLED Micro Lens Array 

A Micro Lens Array (MLA) 4K or 8K UHD screen significantly improves brightness.
It places billions of minuscule convex lenses above OLED panel pixels that redirect more pixel light toward the viewer.

The TV description may not include the term MLA. 
But the highest priced LG OLED screens with high peak brightness specs of up to 1,400 – 1,500 nits are MLA based.
They also include game refresh rates up to 120Hz.

LG OLED EX

Less expensive than MLA panels, and lower brightness, an OLED EX panel offers a 4K resolution with a game refresh rate of 120Hz.
Screen sizes includes 42-inch, 48-inch, 55-inch, 65-inch, 77-inch and 83-inch.

OLED 120 Hz

This panel is an older version of the OLED EX.
It offers 4K resolution at a 120Hz refresh rate with lower brightness levels.

OLED 60 Hz

OLED 60 Hz is the lowest-priced panel. It's similar in brightness to the 120Hz panel.
But it drops the refresh rate to 60 Hz.   It's not the best game choice.

LG WOLED technology has had the lead in the OLED market place.  But the LED race is heating up. 
Samsung reentered the LED race with modified OLED and IOLED technologies.  

Quantum Dot (QD) OLED eliminates the LG color filtered RGB stacked OLED white light concept.  QD-OLED employs a blue OLED layer to excite/illuminate red and green quantum dot film.  Some refer to this as color by blue.  Red and green sub-pixels are produced by the excited quantum dots.  Blue sub-pixels are produced by the blue OLED layer.  This method offers higher brightness, improved contrast, and a broader volume of color.

Select this Link for more QD-OLED information. 

Handbook Samsung QNED Note:
Current publicity does not describe Samsung QNED as inorganic LEDs.  But published QNED Illustrations have listed GaN (Gallium Nitride) as the essential component of the nanorod LED.  GaN crystal is an inorganic substance.

LCD Confusion | LG QNED (LCD) TV and Samsung Neo QLED (LCD) TV

LG introduced a QNED LCD TV.  This may be a good LCD TV, but it is not an IOLED TV.  It is a mini LED full-array quantum dot color filtered backlit LCD TV.

Samsung Neo QLED TV is essentially identical to LG QNED.  Both seem to minimize LCD from their descriptions. Bottom line both are very good LCD TVs.

Micro-LED TV (IOLED) 

Micro-LEDs (not mini-LED) are almost invisible to the naked eye. Red, green, blue micro-LEDs packed alongside one another offer very high-resolution TVs, from 76 inch to 1000 inches.  These wall-sized Micro-LED TVs, referred to as DVLED (Direct View LED), are becoming an alternative to home theater projection systems.

Micro-LED TV promises up to 5,000 nits of brightness, blowing past the brightest OLED, and exceeding LCD sets. Given an LED can be turned off to produce absolute black Micro-LED TVs will achieve new levels of contrast ratio.

Samsung Micro LED Back-lighting LCD TV

This LCD TV appears to approach Micro-LED TV technology.
The backlighting consists of micro red, green, and blue LEDs that are further color-filtered via the LCD panel.
Samsung plans to ship the new TV in late 2025. TCL and Hisense also plan to use this new LCD technology.
Select this TVTech Link for more information.