The moment of a force about any point is defined as the force x perpendicular distance from the line of action of the force to the point - moment = F x d the unit is Nm.
Principle of moments states that for a body in equilibrium the sum of clockwise moments = sum of anticlockwise moments about any point.
F1d1 = F2d2 or W1d1 = W2d2, where W is weight