default sort order

(from github.com/markcamos)
If the General configuration parameter Default Sort Value is blank, what is the default search order of the results?

Also, does the number of clicks on a particular search result increase the score of that document?

(from github.com/marevol)
The default is score.
You can add ScoreFunctionBuilder in app.xml.

(from github.com/markcamos)
What are all the things that contribute to score?

(from github.com/marevol)
See Similarity module.