system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are lumens and candela related and what each represents.

In trying to learn more about each, I was curious if my analogy was appropriate. Is candela sort of like a decibel? In the sense that you can double the lumens, but that doesn't double the intensity of the light. Like four hands clapping isn't twice as loud as two hands clapping.
gpt
A lumen is the total amount of light coming from a source; its "luminous power."  It's equivalent to Watts, the measure of power, but weighted for human vision, e.g., an infra red lamp could put out 100 Watts but, if we can't see it it would be producing zero lumens.  It's a similar idea to the special A-weighted decibel scale ("dBA") for sound that only considers sound pitches that people can hear.

A candela is based on lumens but takes into account how focused the light is.  A plain 1000 lumen light bulb will spread its light evenly in every direction giving about 80 candelas of "luminous intensity" (you divide by 4&times;&pi; because that's the surface area of a unit sphere).  Or you could have a 1000 lumen flash-light that sends almost all its light in one direction, giving off 1000 or even 10000 candela, but only directly in front.  The extreme example is a focused laser beam which can have very high candela ratings with very low lumens.