A lever is a handle, sticking out at an angle, that allows you to operate a machine or close a door . When you pull the lever of a voting booth, you both cast your ballot and open the curtain.
All kinds of things — particularly machines — have levers. The word is also used to describe anything that you are able to use to move or influence someone else: think leverage. A headline in the New York Times said the government would use its contracts with private companies as a "wage lever," meaning the government would try to improve wages by giving work and money to companies that paid well and provided generous benefits. Levers get things done.