The ads were tied to keywords, predetermined by the advertiser. However, the tools that Google provides to help advertisers choose keywords for campaigns are based on historical searches they have performed at some point.
The problem is that according to Google itself, on average 16% of daily search terms are “new” to the browser, or are not contemplated in this historic and practically are not used by advertisers. This creates a huge loss of potential. In addition, companies with a large amount of products with high turnover of stock, also face great difficulties to keep their campaigns up to date with new products, and who have left the air.
Thinking about it, Google launched ads Dynamic Research Network (which is still in Beta). In the new service, the advertiser can link some pre-defined templates for ads to specific pages of the site you want to disclose. When done a Google search and identify a relevant page on your site for it, it will automatically activate the ad by putting the search term in the ad title. Basically Google is failing to use a word to find the relevant page and from page to match the best word.
With that advertisers gain the ability to disseminate products of reduced inventory, just as they are available, without the need for a new structure for a sale that may last only one day. At the same time, users get results that show exactly what they are looking for, even if those keywords in the campaign.
At the same time, dynamic ads will never appear if you have those words in campaign. You will also have choice to deactivate your ads to display dynamic, and even use the terms activated dynamic ads to insert it in your campaigns.