Conversion rate
Conversion rate is the percentage of store sessions that end in a completed order.
Divide orders by sessions over the same period. 300 orders from 20,000 sessions is a 1.5% conversion rate, which is around the middle of the range for most Shopify stores.
Conversion rate is a diagnostic, not a goal. A drop usually points at one of four things: traffic quality, product page clarity, price or shipping surprises, or checkout friction.
Segment before you act. Mobile, desktop, paid and organic often behave differently enough that a single blended number hides the real problem.