In a standard Google AdWords ad, the display URL comes last. This doesn’t necessarily mean it is the least important part – the display URL is an extremely important factor in a user’s decision of whether they click on your ad or not.
Since last week, Google automatically show the display URL domains in ad headlines for selected top placements. The result means business brands are more prominent in ads and the general headline can be used to highlight other important information. If the headline already contains the domain however, it won’t be displayed again.
The new ads have the display URL separated from the rest of the text by a vertical bar and include only the domain (not the “www.” prefix or any subdirectories). The original display URL continues to appear as normal below the description line.
What’s more, it is also possible for the display URL domain to appear in addition to a description line that is promoted to the headline, as long as the resulting headline is sixty-eight characters or less. Phew!
Source: Google AdWords Blog -Showing the display URL domain in the headline for select ads on Google