Rotational Inertia is a measure of the tendency for a rigid, rotating object to continue rotating with the same velocity about the same axis is a result of rotational inertia. The rotational inertia depends on the mass of the object and how far the mass is from the axis of rotation. The farther it is from the axis, the greater the inertia.
Angular momentum is the rotational inertia times the angular velocity.
The angular momentum of an object will not change unless an external torque acts on it. A force can exert a torque about an axis. The torque is the force times the distance f rom the axis. It tends to rotate the board counterclockwise about the fulcrum. If the force were on the other side of the fulcrum, it would tend to rotate the board clockwise about the fulcrum.