Borders is a defunct book store in the USA. They also had an eBook store at (link now goes to Barnes and Noble) http://www.borders.com. This store was driven with Kobobooks software and they sell a Kobo reader that uses a modified configuration that points its web access to their store instead of the Kobo web store.
Borders is not one company its actually three: Border's Book Group - which owns the other two companies, Border's Book Stores, which recently filed for chapter 11 while shutting down 200 stores, and Borders.com, which runs the web site. The web site seems to be directed to Barnes and Noble at the end of 2013 so I would think Borders is totally gone.