The Dink Network

They're different. If someone asks you whether you want to eat apples or oranges, replying with "either apples or oranges" means apples or oranges, and "neither apples nor oranges" means not apples and not oranges. I think most people think of either as exclusive, so they mean "apples or oranges but not both." In programming, I believe either (for things like the || operator) is typically inclusive, so it means "apples or oranges or both."

Edit: Quiztis's answer is also true. The words either and neither have several different usages.