SEO is an acronym for Search Engine Optimization.
It allows search engines like Google to find and categorize a website. You can read more about the technology HERE.
Each vendor can set the SEO for their store so as to increase the search ranking of their store. That way customers are able to find their products easier and faster.
To set the SEO, open the Store Manager, click on Settings and then SEO.
Enter the information for the General, Facebook and Twitter Setup.
Click Save when done.