An e-commerce platform is the software on which a brand builds and runs its online store. It holds the website, the catalogue of products, the cart and the orders. It is also called a store builder or an online store platform. Shopify is the best-known example, and many Indian D2C brands build their stores on it.
The brand does not install anything. It pays a monthly fee, and the platform company runs the store on its own servers. Software rented like this is called SaaS, software as a service. The brand picks a theme, which is a ready-made design for the pages, and adds its products, prices and photos.
The platform does four core jobs. It shows the catalogue: each product, with its sizes, colours, price and stock. It keeps the cart, the list of products a shopper has chosen. It records every order and sends the shopper a confirmation. And it keeps the stock count, so that a sold-out size cannot be ordered again.
Everything else is added through apps. An app here is a separate product, made by another company, that the brand switches on from the platform's app store. The app reads and changes the store's data through the platform's APIs, the fixed ways in which one program can ask another for data or give it an instruction. For instance, a shipping app can ask the platform for every new order, and then add the courier's tracking number to each one.
Take, for example, a handloom saree brand in Varanasi that starts selling online. In one week, it lists 120 sarees, each with photos and a price between ₹3,500 and ₹18,000. It switches on a one-click checkout app, so that shoppers can pay by UPI or choose cash on delivery. It connects a payment gateway to receive UPI and card payments. It adds shipping software, which books a courier for each order and prints the label. An indirect tax app adds the right GST to each invoice. When a shopper in Bhopal orders a ₹6,200 saree, the platform records the order, reduces that saree's stock from one to zero, and passes the order to the shipping app.
Not every seller uses the same kind of platform. Some Indian platforms are built for small sellers, with shipping, payments and marketing already included, so the seller does not have to choose apps. Large retailers need more. Their platform also connects to the billing counters in their shops and to an order management system (OMS), which decides whether a shop or a warehouse sends each order.
A platform is different from a marketplace. On an online marketplace, thousands of sellers list their products in one app, and the marketplace holds the shopper's details. On its own platform, the brand controls the store's design, keeps the shopper's details and sets its own rules for prices and returns.