What does Candela mean?

Candela is the SI unit of luminous intensity, measuring the amount of light emitted in a specific direction by a light source such as your light bulb. It is used to quantify the brightness of a light source.

1 Candela is equal to the light emitted from a single candle at a 1-meter distance. When the light bundle becomes more concentrated, the luminous intensity will become smaller. As Candela represents the light stream between a beam angle, the intensity (or the amount of Candela) will be higher in a smaller light bundle.

The reason why Candela isn't mentioned on all lights has to do with the fact that a regular lamp emits its light from every angle. measuring units like Candela are only applicable to light sources with a specific angle feature like lighting spots or reflector lamps.

The relation between what is mentioned above in one picture: