In Magento 2 Marketplace, the sellers can create two types of product SKU ie; Static and Dynamic as per the admin configuration from the backend.
When the admin has set “Allow seller to add products with SKU type” as “Static”.
Then, the sellers can create the product SKU while creating the product as per their choice.
And can also get to know whether the product SKU is available or not.
When the admin has set “Allow seller to add products with SKU type” as “Dynamic”. The admin will also define the SKU prefix.
Then, the sellers will not have the types of product SKU field while creating the product. It will get created automatically. After saving the product, the product SKU will be visible on the frontend.