Atariff is a form of taxation on foreign products, while a quota is a on imports from foreign countries.

Limitation

Explanation:

The tariffs are a form of taxation for foreign products. The main reason behind the tariffs is to protect the home producers from foreign competition, thus protect the home economy. On the other side, the quota is not something that is falling under the taxation, but it is actually a limitation, and that can go for any product. The quota limits the amount of products that can be imported from a certain country, that can be food, machines, movies, clothes etc. A nice example of this is China, where the country has quota on US produced movies, with only 24 movies allowed to be shown in the country per year.