What is conversion rate optimisation?
If you are in e-commerce you will be familiar with the conversion funnel, which is the journey that a customer will take through your website before converting to a sale. In general the fewer steps you include in your conversion funnel, the higher the final conversion rate.
For example, an ad on a search engine may have a 10% conversion rate. An email newsletter typically converts at 1% while a followup after a sale may convert at 5%. These numbers tend to increase dramatically if you pick the right time and day, or target a customer just after interacting with them.