How online stores actually work, taught as the learnable skill it is — through name-the-mechanic, spot-the-error, and best-choice scenarios with one defensible answer, never a promise of results. Conversion-rate optimization and the funnel from visit to purchase, product pages that sell (images, benefit-led copy, reviews, a clear call to action), the cart and checkout and why shoppers abandon them, pricing and promotions (anchor and charm pricing, the economics of a free-shipping threshold), the unit economics that decide whether a store makes money (average order value, customer acquisition cost, lifetime value, return on ad spend, and contribution margin — many computed), selling on marketplaces (Amazon, eBay, and Etsy mechanics, the Buy Box, fulfilled-by-Amazon versus merchant-fulfilled), storefront platforms, traffic and acquisition, email and SMS lifecycle flows and retention, fulfillment and shipping, returns and customer service, inventory and operations, the analytics that diagnose which problem you actually have, trust and payments and fraud, the legal essentials (the FTC’s disclosure rules and how sales-tax nexus works), and the growth strategies — and myths — of selling online. Every explanation names the principle, the tempting mistake, and a rule you can use. Distinct from Marketing (demand generation), Sales (one-to-one selling), and SEO (search ranking): this is about running the store itself. Educational skill practice in how e-commerce works — never business, financial, or legal advice, and growth is never guaranteed.