Quoting from the blog, "Whereas many other military records provide information about officer-class soldiers, these records relate to ordinary, non-officer class soldiers. This makes it more likely that you will be able to find details about your ancestors. The connection with 'Chelsea Pensioners' is that the pensions were administered through The Royal Hospital at Chelsea. The great majority of pensioned soldiers were out-pensioners and did not reside at the Hospital itself."
You can read more at http://blog.findmypast.co.uk/2010/05/chelsea-pensioners-british-army-service-records-1873-to-1882-now-on-the-site/