What it is
E965 is maltitol, a sugar alcohol made by hydrogenating maltose (which comes from corn or wheat starch). NOT to be confused with E966 lactitol which is dairy-derived.
Why it matters
Sugar-free chocolate, sweets, and chewing gum. The closest sugar-like sweetness of any sugar alcohol.
What to do
Always vegan. (E966 lactitol is the one to avoid.)