Lumen (lm) is the unit for the total amount of light that a lamp emits in all directions.

• The number of lumens on a lamp indicates how much light the lamp can produce, but does not indicate how much light actually falls on a surface.

• To know how much light reaches a particular surface, you use Lux (lx).

In short: lumens tell you about the total light output of a lamp, while lux indicates how much of that light is available on a surface.