Homeopathy refers to treatment of symptoms by extremely diluted versions of poisons that are thought to create those symptoms. I'll defer to The Amazing Randi for a nice explanation of why that doesn't make any sense.
My favorite part: "Non habit-forming." Except for the people who have a habit of buying homeopathic "remedies."
Mole at Wikipedia for the unit of substance.
Avogadro's constant at Wikipedia for the number of atoms or molecules in a mole.
- Updated video link.