To put it simply, tariff are trading barriers that impose a tax on bot import as well as export goods. Custom Duty tax is one such commonly applied tariff. Non-tariff barriers are those regulations or restrictions faced on certain goods during import or export which do not involve taxes/tariffs. These can be any kind of regulations like licenses, standards, quotas and many more.
Tariff are taxes applied on import goods which helps in restricting import and trade in the country. On the other hand, non-tariff are government policies or practices which restrict import and trade in the country. Non-Tariff are not taxes but regulations which need to be followed like standards, quotas, licences, etc.