Drop shipping is a retail model, where a reseller accepts an order without having a product in their inventory. They forward the order to the product's supplier, manufacturer, or another reseller who then ships the order directly to the client. They make a profit out of the commission set on the product. In white labeling, the products are kept in the inventory and sold under the store's brand. The client usually doesn't know they are buying a resold product and think that it was created by the brand they bought it from.
Both options are much cheaper than having a private label, with drop shipping being even risk-free and with low-investment costs. White labeling requires investing some more resources, but that's the price that you must pay for product branding. It's worth remembering that thanks to this investment, you will be able to sell the same product for more money than in the drop-shipping model.