As we don’t all know, an ion is an atom or molecule whose total number of electrons and total number of protons is not equal. Thus, it has a positive or negative charge.
One rule-breaking special case of ions is the* zwitterion*[footnote]From ‘zwitter’, meaning hermaphrodite in german.[/footnote]. It’s a neutral molecule (no net charge), but contains both positive and negative charges. Huh…?
Imagine one branch of the molecule as negative and another as positive. Separately they’re charged, together they’re balanced. The Zwitterion.