Hey Mario,
Custom link reports are generally used to perform a comparative analysis on different links on a page. For example, on Sports page of a website, they are multiple links related to Cricket that takes a user to espncricinfo.com, say one is a simple link, other is embedded in an image. You could analyze the numbers against those links to see which is performing better.
Further, to analyze, the page URL breakdown would give the URLs. Additionally, you could analyze the parameter "pev2" (it specifies the link name) in the server call (using debugger). Or, if you pass that in an eVar or prop, you could break the custom links by those as well.
Hope it helps!