What is the difference between active and passive voice in these sentences?
This product is sold well.
This product sells well.
What is the difference between active and passive voice in these sentences?
This product is sold well.
This product sells well.
The difference is between the passive voice, which implies that a seller exists and the active voice, which does not. "sell" is one of those verbs in which context determines the role of the subject.
The product is selling / John is selling (the product)
However in the passive voice, only the transitive form of the verb is possible:
The product is being sold (by John)
So the difference between the passive and active is the implied role of the (unnamed) seller.
The product is sold well (by John)
This tells us that "John" is doing a good job. You would not normally use this structure, as the active voice is better suited. "John is selling the product well."
The active form has no implied seller, so it just means that lots of people are buying the product.