One footcandle is the illumination produced by one lumen uniformly distributed over one square foot of a surface, or conversely this is the illumination at the point of a surface which is one foot from, and perpendicular to, a uniform point source of one candela. Lux is used in the International System. Both have a similar objective, but meters are used for Lux and feet are used for Candelas. Luminance or Brightness is a luminous intensity of a surface in a given direction per unit of projected area of the surface. Actually, our eye sees brightness, not illumination.
Every visible object has brightness.
Usually, brightness is proportional to the object's illumination, so a well illuminated object seems brighter. One footcandle is the illumination produced by one lumen uniformly distributed over one square foot of surface, and lux is the illumination over one square meter of surface. This website will convert footcandles into other light measurements and vice versa.