Brightness can be measured in one of two ways: in candela or lumen.
Candela is a measurement unit that describes how intense the light is. The higher the candela, the farther you can be from a target and still see it clearly.
On the other hand, lumen is the standard measurement for brightness. It is the more popular out of the two. It measures the brightness from any point in the direction away from the light.
You’ll find more use out of lumen and most manufacturers will give you this number. Candela is still used by many out there. In that case, just convert the candela to lumen if you want to know exactly how bright it is in the standard measurement. 1 candela = 12.57 lumens.