A more thorough explanation:

The Import-Export Clause is a provision in the United States Constitution, specifically in Article I, Section 10, Clause 2. This clause prohibits states from imposing taxes on imports or exports.

For example, if a state wanted to tax goods that were being imported from another country, they would not be allowed to do so under the Import-Export Clause. Similarly, if a state wanted to tax goods that were being exported to another country, they would also be prohibited from doing so.

However, the Supreme Court has interpreted this clause in a way that allows states to tax imports as long as the tax does not discriminate in favor of domestic goods. This means that a state can impose a tax on imported goods, but they must also impose the same tax on similar domestic goods.

For instance, if a state wanted to tax imported cars, they would also have to tax cars that were made in the state. This ensures that the tax is not unfairly targeting foreign goods and is instead being applied equally to all similar products.