I don't get conversions

In electronic commerce, conversion marketing is marketing with the intention of increasing conversions--that is, site visitors who are paying customers. The process of improving the conversion rate is called conversion rate optimization.

It is a noun. The definition of a conversion is a change from one religion to another or adopting a religion. An example of conversion is a Catholic switching to Taoism. A conversion is defined as an exchange from one unit of measure to another. An example of conversion is exchanging dollars for euros.