Both terms refer to a choice involving two options. Let's say you have option A and option B. To choose EITHER A or B means you must choose one; you cannot have both. If you choose A you cannot also have B. To choose NEITHER means that you do not choose Aor B. You refuse both of them. If you're a math or logic person, either allows us to use the "Exclusive Or," in everyday speech; some might call it XOR. If I could "choose A or B," I would have the option to choose just A, just B, or both A and B.

Hola Meli, Neither es como ¨tampoco¨ en español, no opta ninguna de dos partes. Pero Either tiene un sentido de seleccionar una de A y B.