The 2nd row in dash are programs that are the default programs (*) or have been used by you. I did not get this in the beginning either but dash is not a search tool but it is a 'you used this alot before so I show it to you now too'-tool: Dash automatically changes content based on what you use.
If you have firefox as a browser in dash and remove firefox, then add chromium dash will not show chromium (you did not use it...) but after using chromium it does.
(*) to change the default have a look at preferred applications for some options:
Sidenote: you can add activity journal to add some insight in zeitgeist/dash-usage: