There are a lot of different methods to sell online.
1. You sell via third-party marketplaces like amazon, eBay, Etsy, Zazzle etc.
2. You manufacture or procure products and sell products from your own store
3. You dropship
4. You sell products as an affiliate marketer
For the first and second method, you need to maintain your inventory, you either have to manufacture your products, or procure products, create a listing on the site where you are selling, and market your store to drivesales. In the third method, or the dropship method, you sell from your own store, however, you don't sell your own products, you don't have an inventory. What you do is you create a listing, you sell products and the forward the shipping details to the supplier who actually packs the product and ships to the buyers' address. The fourth method, or the affiliate marketing method, also does not require you to have your own product, you refer people to seller's store and you earn commission for each sale. Of all these 4 methods, the fourth method is easiest and cheapest, in most cases you don't even need a website. However, having a website can be better.
Now, if you want to sell online, which method do you choose?