A standard dimmer reduces the RMS voltage going to a light to dim it; this may be done by a simple resistor or by chopping of the top of the waveform. So a dimmable LED bulb must be able to:
Cope with a big range of input voltage including part formed sine waves, which isn't easy for the control logic. Detect from the input voltage the light level that the user wants, and then give that light level.
It would be a lot better if a dimmer switch could send a digital signal (radio, or over the main wiring) to the lamp, so that the LED light could know what was required without reverse engineering the voltage back to the user's wishes. However this would need a new standard to be used by all switch and LED Panel Light vendors, so may take a little time.
Your "standard" dial or track dimmer is either just a big potentiometer or Rheostat that reduces voltage through resistance, or a slightly more efficient design called a TRIAC dimmer, which uses a specialized transistor design to attenuate the line voltage by turning the line on and off based on where the AC is in its "rhythm" or "phase".