Multi-vendor application using Magento - that means seller or vendor can register in to your magento store and they can upload the product , manage the inventory , manage the orders and can manage the shipping . there are various kind of multi vendor marketplace example seller will be able to add a new product or old product or seller can choose the existing product from global catalog .
even in advance concepts - marketplace vendor can also ship their product using dropshipping i.e admin can assign particular vendor to a dropshipper and order and delivery management will take place from dropshipper
Dropshipping using Magento - in this case you dont need to create a marketplace , what will happen lets say you create your own store and you dont want to have a warehouse of product in this case dropshipping is super useful . that means when ever a order will come in to you site , shipment and order will be managed by dropshipper .
admin need to add dropshipper and admin can add what shipping methods dropshipper provides and during checkout buyer can choose the shipping methods . so in this case all the delivery will be managed by dropshipper your store will be kind of a front end where you will get % of payment in every sale (its depends on your business modal how do you manage it ) .
PS - we are creating marketplaces for magento , this is not an advtisement but you can check more feature what a multi vendor product should have at this link https://store.webkul.com/Magento-Marketplace.html