What is Comparison Shopping?
The Comparison Shopping Service (CSS) program was created by Google in 2017 to diversify the search results for Product Listing Ads (PLA) sometimes referred to as “Shopping ads” or “Google Shopping”.
Long answer is that in 2017, after a lengthy procedure, Google received a record fine of 2.4 billion Euro by the European Commission for abuse of power. What Google did was considered ‘illegal under EU competition rules’ in accordance with this ruling. Google created a platform for advertising with shopping ads on its search results page, which was only accessible to web shops, hereby depriving other parties (comparison sites) of the opportunity to compete fairly. The opinions in the industry differ on whether this statement is justified or not, but at least Google was very keen to change this. If Google did not implement major steps towards embracing comparison sites, the fine would have been increased by around 5% of its worldwide revenue per year. Google then initiated those steps with the launch of the Google CSS program.
You can read whole statement of the European Commission here.
In short:
We offer a tool that saves up to 20% of the advertising price based on a legal dispute, which Google lost to the EU.