The 3 main stages in the development of eCommerce are planning, building, and launching. Planning involves researching the market and determining which products are in demand, as well as creating a business plan for success. Building involves selecting the ideal platform for your shop, selecting themes, designing user interfaces, and adding necessary components like payment processing options. Launching is when everything comes together: completing testing and promotion, announcing the launch date to customers and partners, managing orders and shipping, and marketing the store.