Those are almost certainly HIPAA formats, i.e. ASC X12 270 ASC X12 271 ASC X12 834 ASC X12 837

A very brief overview:

http://healthit.hhs.gov/pdf/electronic-eligibility/appendix-e.pdf

You need to ask for the general ASC X12 "Implementation Guide" as well as the "Companion Guide" from whoever is generating the file in question - code for one 271 file may not work for another 271 file.

And example "Companion Guide" - DO NOT USE THIS ONE FOR YOUR PROJECT.

http://www.cms.gov/Research-Statistics-Data-and-Systems/CMS-Information-Technology/HETSHelp/Downloads/HETS270271CompanionGuide5010.pdf

Note that a correct implementation is significantly more difficult than a minimally working implementation for a single file - look for third party products or another language entirely. The meaning of different segments depends on context, not all fields are always filled in, and it gets more interesting from there. There should also be loop counters (make sure you understand the loops, as well).