Conversion rate
Conversion rate is the share of people who take the step you wanted, out of everyone who had the opportunity to take it. Enquiries out of website visitors, bookings out of enquiries, repeat customers out of first-time ones. It is only meaningful when you are specific about which step and which group you are counting.
Why one number is usually the wrong number
A single site-wide figure hides where the loss actually happens. Splitting the journey into steps — visited, enquired, booked, showed up, bought again — turns a vague sense that things could be better into one identifiable place where most people stop. That step is where the work belongs, and it is frequently not the one that felt obvious.
The trap of improving the wrong step
A better conversion rate on a step nobody reaches changes nothing. Before optimising, check the volume flowing into the step: the largest absolute gain is usually at the step with the most people, not the one with the worst percentage.