The discipline of lifting the percentage of visitors who buy, by improving the store rather than the traffic. CRO is the cheapest growth lever you own: a relative lift in conversion rate flows straight to revenue at no extra ad cost, and it lowers effective CAC at the same time. It starts with the product page, the path to checkout, and removing friction, not with button colours.
Benchmark. The Shopify median sitewide conversion rate is ~1.4%; 2-3% is solid, and 3%+ puts you in the top 20%. Mobile usually converts 40-50% below desktop despite carrying most of the traffic, so that gap is where the money is.