Google AdWords "Enhanced Ad Sitelinks" works by incorporating text from ads in your account that are related to your sitelinks.
"To be eligible, your ad with sitelinks must show above Google search results and your account must contain active ads closely related to the sitelinks in your campaign," mentions Google.
Adding, the team said, in testing, people reported that ads with enhanced sitelinks were more useful and relevant. And clickthrough rates were significantly higher than the same ad with traditional 2- and 3-line sitelinks.
"Ad Sitelinks give users more options, and deliver advertisers more clicks. On average, the clickthrough rate is 30% higher for ads with sitelinks than those without," Adwords team stated.
"For example, say you've created sitelinks for your pizza restaurant campaign, and your ad displays sitelinks as shown here:
Now, let's say your account also includes the following text ads:
With this enhancement, your ad could now look like this," explains Google:
If you're not already using ad sitelinks, to get started, please visit AdWords Help Center.