Drop shipping is a supply chain technique where the retailer does not keep goods in stock. The retailer transfers customer orders directly to the supplier who then ships the product directly to the customer.  The easiest way to set this up is through a middle man such as Doba. Companies like Doba build relationships with multiple manufactures and provide a site for you to buy these products at wholesale for a membership fee. The idea is that they buy products on behalf of all their members so you should get a better price than if you negotiated directly with the manufactures yourself.

It works like this:
Set up a website that uses a drop ship friendly shopping cart and merchant account. 
Find wholesale suppliers of products you wish to sell that utilize the drop ship business model.
Gather content and images about your products and place them on your site and shopping cart.
Collect the order and payment from your website.
You in turn pay the wholesaler and they fulfill the order and send it to your customer.