Korth wrote:
Normal (monochrome) LEDs each have two wires, power and ground. They're "dumb", they light when powered, their brightness can be controlled by varying voltage.

4-pin RGB LEDs each contain an individual Red LED, Green LED, and Blue LED in a single discrete package or module. One wire to power each of the RGB colour "channels" plus one common ground path. They're still dumb but different voltages on different channels can mix into a spectrum of colour combinations. 5-pin RGBW LEDs are a common variant, adding a White LED component (and colour channel) to the package.

Addressable LEDs each contain an IC in their package or module. They only respond to power during a specific frequency-divided time window. The idea is to rotate each LED address through a cycle with more power across less time to maintain overall brightness, an LED strip with ten addressable components would always have one component lit at ten times overall intensity while the other nine components are unpowered.
(This is a simplification. Address switching frequency is normally hundreds of KHz, response time for each hardware address is normally plus/minus hundreds of ns, different LED semiconductors always have particular "ignition" and "sustain" and "fade" properties which blur into a "persistent illumination" effect when switched at these sorts of frequencies. Multiplexed power/timing signals can produce complex striping, chasing, strobing, and shifting transition effects by "simultaneously" addressing multiple LED components with different colour information.)

Korth wrote:
The "simple English" ...

Non-addressable RGBs, the whole strip/array of RGB LEDs displays one colour at any time. This colour can transition, shift, breath/pulse, etc, across the entire RGB LED colour spectrum - and AURA provides a variety of snazzy themes/effects - but every RGB LED is always exactly the same colour as all its neighbours at any given instant, the whole strip is "all or nothing".

Addressable RGBs, each RGB LED (or segment/block of RGB LEDs) can display a different colour and intensity than its neighbours. Some could be lit in one colour or lit in another or more intense or less intense while others are simultaneously displaying something else. Everything that non-addressable RGB does but more fancy animation/striping/chasing effects are possible. Higher cost and complexity.

Each of these little LEDs uses a tiny amount of electrical power when lit and they all add up, there are limits to how many you can daisy chain or branch off each motherboard header.

https://rog.asus.com/articles/guides/video-guide-how-to-install-aura-rgb-lighting/
https://rog.asus.com/articles/maximus-motherboards/all-new-aura-lighting-control-and-rgb-strip-heade...
https://www.asus.com/ca-en/Motherboard-Accessory/ROG-Addressable-LED-Strip/

Z270/MAXIMUS IX APEX = not addressable (I think)
Z370/MAXIMUS X APEX = not addressable
X299/RAMPAGE VI APEX = addressable

I wouldn't personally make (addressable) RGB LED a priority when selecting a motherboard. For me it's just a "nice to have" but very optional and very much less important than other motherboard parameters (one of which is cost, assuming all other things are equal). Fully addressable RGB functionality can always be added later through chassis or add-on accessories, if/when needed. But I do understand that my priorities aren't for everyone.