Conversion Rate Optimization (CRO) involves methods used to improve the effectiveness of a website by increasing the percentage of visitors who complete a desired action. This could be making a purchase, signing up for a newsletter, filling out a contact form, or clicking on a link. CRO uses various techniques like A/B testing, user feedback, and analytics to understand visitor behavior and identify barriers to conversion. The goal is to make the website more user-friendly and persuasive, enhancing the user experience and ultimately leading to more conversions.