关于墨西哥离境税，还有Volaris航空

请问从美国到墨西哥有没有入境税啊？
因为我在Volaris官网买机票，洛杉矶-墨西哥城，在选择国籍的时候，会出来一段字：Remember that as per official disposition, foreigners that visit Mexico must pay the Non Resident Fee (DNR), which is automatically added to the reservation taxes and will be reflected in the subsequent steps.
然后继续往下后，最后税费那里会多一个 UK Tourism Tax (UK) ，大概21美金左右，请问这是什么税？？？