Courtesy of Curiosity.com:
“If we asked you to cut a piece of bread in half with only one cut, could you do it? Sure you could. You could probably cut an entire ham sandwich in half just as easily. But if we knocked over the plate and left the bread and a single piece of ham in a big mess, could you cut them exactly in half with a single cut? There’s a mathematical principle that says, yes, that’s technically possible. It’s called the ham sandwich theorem. What else would they call it?