It's basically everything you can do in order to increase conversion rate on your website. There are lots of different techniques. For example, you should work with the title and description to increase CTR, match user intent, elaborate the conversion process within your website (make it easy), make your call-to-action stand out, show unique selling proposition etc.
In the online marketing world, conversion rate optimization (aka web analytics conversion optimization) is a strategy for increasing the percentage of visitors to a website that converts into customers, or more generally, takes any desired action on a webpage. It is commonly referred to as CRO.
Conversion rate optimization (CRO) is the systematic process of increasing the percentage of website visitors who take the desired action be that filling out a form, becoming customers, or otherwise. The CRO process involves understanding how users move through your site, what actions they take, and what's stopping them from completing your goals.
Conversion rate optimization is important because it allows you to lower your customer acquisition costs by getting more value from the visitors and users you already have. By optimizing your conversion rate you can increase revenue per visitor, acquire more customers, and grow your business.
Conversion rate optimization is the process of increasing the percentage of website visitors that convert on your site. For instance, if you have a 25 percent conversion rate, that means 25 percent of people who visit your website actually convert. It's kind of like running a retail store.