Other Quotas: There are several kinds of quotas for tickets for various special categories of passengers, other than the quotas for intermediate stations mentioned above, ticket agencies in other towns ('OS' = Out-Station quota), etc. These include small numbers of seats and berths set aside for railway officials ('HO' = Head Office quota ('High Official' quota)), ministers and high bureaucrats as well as members of parliament and their staff ('PH' quota ('Parliament House')), defence officials ('DF' quota), foreign tourists ('FT' = Foreign Tourist), handicapped travellers ('HP' = Handicapped Person), railway staff on duty ('DP' = Duty Pass) (this has its own waiting list, the 'DPWL' or Duty Pass Waiting List, especially for railway staff travelling on Privilege Passes on Rajdhani trains), women travellers ('LD' or 'LQ' = Ladies Quota), and those needing to travel for extremely urgent reasons ('EQ' = Emergency Quota), etc. Each one of these quotas can theoretically also...
more... have its own waiting list, usually denoted by the quota abbreviation followed by 'WL', e.g., FTWL, EQWL, HPWL, etc. RAC or Reservation Against Cancellation (see above) is technically not a quota, but is often shown as one, as 'RC' quota.
Source irfca.org/faq/faq-travel.html