In general, I want to understand for myself how beneficial this is. Who does this and how do you resolve issues?

This type of business requires virtually no initial capital, therefore, the intermediary does not bear any risks. He will give his money only after he receives payment from the buyer.
The intermediary does not require warehouse premises for trading. All he needs to run his business is a computer with Internet access. Companies like Selpway Trading help set up the process.
The supplier takes care of all the shipping of the goods. Who benefits from this, everyone decides for himself!

Ok, thanks for the short and clear answer!