It used to be (or still is inside Box?) an analytics startup [1][2][3].
EDIT: Their Twitter account also gives a little bit of information: Wagon is a modern SQL editor. A better way for analysts and engineers to write queries, visualize results, and share data & charts [4].
It is(was) a company and its main product was a SQL client with built-in visualizations and features to save queries (just the query not the RS) in their cloud and share these queries with others peers in your organization.
In my opinion it was a very good product... Sad that they didn't open sourced it. =/
EDIT: Their Twitter account also gives a little bit of information: Wagon is a modern SQL editor. A better way for analysts and engineers to write queries, visualize results, and share data & charts [4].
[1] https://www.wagonhq.com/about
[2] https://www.wagonhq.com/blog/engineering-at-wagon/
[3] https://www.reddit.com/r/haskell/comments/37jwip/a/
[4] https://twitter.com/WagonHQ