The conversion rate refers to the percentage of conversions made based on the total number of visitors.
A conversion can be various actions that you want the user to take (purchase, registration to a loyalty card, purchase of a product on promotion...).
For example with ToucanToco our goal is to have site visitors click on the "free demo" button, so we calculate our conversion rate by dividing the number of users clicking on our "free demo" button by the total number of visitors to our site and we get our conversion rate.
Monitor this KPI is essential to measure the effectiveness of each marketing and trade action implemented. From a comparative perspective (between several stores in a given region, for example), measuring this data makes it possible to identify good practices and extend them to all your stores.