The number is meaningless without naming both halves. "Our conversion rate is 3%" could mean visitors who sign up, trials that become paid, or leads that become customers — three different problems with three different fixes. Define it as an explicit pair: from what, to what, over what period. Then track each step separately rather than collapsing them into one headline figure.
It matters because conversion is usually the cheapest growth lever a small business has. Doubling traffic costs money and time; improving a checkout page from 2% to 3% delivers the same result by the end of the week and keeps working. It is also a diagnostic. A high visitor-to-trial rate paired with a low trial-to-paid rate says your marketing is honest and your product is not yet convincing — the opposite pattern says you are attracting the wrong people entirely.
A concrete example: 4,000 people visit your pricing page in a month, 240 start a free trial (6%), and 36 of those become paying customers (15%). The overall visitor-to-customer rate is 0.9%. Lifting the trial-to-paid step from 15% to 20% adds 12 customers a month with no extra traffic. Lifting the pricing page from 6% to 7% adds only about six. Same effort, and the numbers tell you where to spend it.