Split testing allows you to try out several versions of specific page (typically a landing page) on your visitors and then analyze the results to see which one performed better. For example, which landing page led to the highest percentage of people signing up for your service.
Clicky doesn't do your split testing for you, e.g. showing different versions of a page to different visitors. What we do offer is an API that lets you inject your site's split testing information into your Clicky reports, and optionally (preferrably) link the tests to specific goals on Clicky so you can see which versions of a split test are leading to the most conversions.
Visual Website Optimizer
both have integrations with Clicky, so you don't have to worry about any coding. Otherwise, you'll want to read the links below.