Article / Updated 05-23-2018
In addition to Marketplace, many people use Buy/Sell Groups on Facebook to buy and sell used items. You can use both (and, in fact, Facebook makes it easy to post Marketplace listings to Buy/Sell groups you belong to and vice versa). Usually people tend to use Buy/Sell groups for the following reasons:
Groups require membership: Because members of a group must actively join that group, this acts as a bit of a filter on both the number of people who will see your listing and the type of buyer/seller you are interacting with.