The way levers operate is by an effort applied at a point, which moves a load at another point through a balance point called the fulcrum. It is the relative positions of these three points - the effort, the load and the fulcrum - that distinguishes the type or class of lever. There are three classes of lever 1st, 2nd and 3rd class.
First class lever
In summary, in a first class lever the effort (force) moves over a large distance to move the load a smaller distance, and the fulcrum is between the effort (force) and the load. As the ratio of effort (force) arm length to load arm length increases the mechanical advantage of a first class lever increases.
Second class lever
In a second class lever the effort moves over a large distance to raise the load a small distance. As the ratio of effort (force) arm length to load arm length increases, the mechanical advantage of a second class lever increases. In a wheelbarrow, the closer the load is to the wheel, the greater the mechanical advantage. Nutcrackers are also an example of a second class lever.
In a third class lever the load moves further than the effort (force) and the mechanical advantage is low, which is why it's difficult to apply great force to the load. This can be an advantage by not squashing sausages on the barbecue!
When you lift a load using your forearm you are using a third class lever. Your biceps muscles are attached to the forearm just in front of the elbow. The load is on the hand, and the effort is between the fulcrum (elbow) and the load.