A leg is the part of a person's body that they use to walk around. All legs, including those of humans and tables alike, are meant to support.
Your leg is the appendage that stretches from your hip to your ankle, bending handily at the knee so you can run, walk, jump, sit, and skip. You probably also use the word leg to refer to one side of your pants; a support holding a table up; and one separate section of a long trip: "I'm stopping for coffee on the next leg of my journey." Leg probably comes from a Proto-Indo-European root meaning "to bend."