Buyers can send messages to vendors on the marketplace either from the vendor's store page or from the product page. When a buyer sends a message to the vendor, the message will show on the 'Buyer Support' page.
Here a vendor will be able to respond to buyer's emails, and either keep open the communication with the buyer or close the ticket after the question has been answered.
This is a good way to keep track of buyer's requests and questions. Even after closing a ticket, vendor will have access to previously closed tickets.
This feature should not be confused with the Quotation feature.