Google have been updating the design and experience of Google Search to give users a "more seamless and consistent online experience".
Search ads that have previously shown to the side of the results may in some cases appear at the bottom of the page.
This is very similar to the current search landscape seen on mobile search.
You can see the performance of your ads in a Top V Side segment report. With this launch, all side, bottom and experiment impressions will now be classified as "Other" so you can more easily see how your top ad placements perform against placements on the rest of the page. In the coming weeks, "Top vs. Side" will be renamed to "Top vs. Other."
One of PPC Experts Luke has written a couple of blog posts on this subject: