Short answers, pulled from the story.
A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, called a fulcrum. It is a rigid body capable of rotating on a point on itself, and it is one of the six simple machines identified by Renaissance scientists.
The Greek mathematician Archimedes is credited with the statement "Give me a lever (long enough and a fulcrum on which to place it), and I shall move the world". The earliest remaining writings regarding levers date from the third century BC and are attributed to him.
Levers are divided into three classes by the relative positions of the fulcrum, effort, and resistance. In Class I the fulcrum is between the effort and resistance, in Class II the resistance is between the effort and fulcrum, and in Class III the effort is between the resistance and fulcrum.
The law of the lever states that the ratio of output force to input force equals the ratio of the distances from the fulcrum to where those forces are applied. If the input force is applied farther from the fulcrum than the output force, the lever amplifies the input force.
The word "lever" entered English around 1300 from the stem of the verb lever, meaning "to raise". It traces back to the Latin levare and the adjective levis, meaning "light", and ultimately to the Proto-Indo-European stem legwh-, meaning "light", "easy", or "nimble".
The malleus, incus, and stapes are small bones in the middle ear that are connected as compound levers. They transfer sound waves from the eardrum to the oval window of the cochlea.