On your own website, you control the design, the SEO, and the checkout experience end to end. On a marketplace, you're working inside someone else's rules — fixed listing templates, platform-controlled search ranking (Amazon's A9, Flipkart's catalog score, Myntra's style filters), mandatory compliance fields, and account health metrics that can restrict or suspend you if ignored. The keyword strategy is different too — buyers are already inside the marketplace with high purchase intent, so visibility depends more on listing quality, pricing, reviews, and ad spend than on traditional SEO. Each marketplace also has its own seller dashboard, claim process, and ad system, which is why managing several platforms well usually needs a dedicated team rather than a single generalist.