If you're after the difference between customs duties and excise duties then I think, as a general rule, that customs duties are levied on goods brought into the country whereas excise duties are levied on goods produced within the country. There have been some odd excise duties over the years though, including taxes on windows, candles, playing cards, manservants; even an excise tax on railway passengers. So the rule of thumb does not always work, like a lot of definitions steeped in history.