The lumen is a measure of the total "amount" of visible light. The lumen is the SI derived unit of luminous flux (symbol: lm).
The candela is power emitted by a light source. it is the SI base unit of luminous intensity ( symbol: cd).
A full sphere has a solid angle of 4·π steradians, so a light source that uniformly radiates one candela in all directions has a total luminous flux of 1 cd·4π sr = 4π cd·sr ≈ 12.57 lumens.