The 'DB' or 'D' generally, but perhaps not always, indicates dual-brake capability. 'HS' may be for 'high speed'.'2S', '3P', '6P', etc. indicate traction motors connected in series or parallel. The WAM-4 locos were later reconfigured to have all motors always in parallel (6P variants) or with the three series-connected pairs in parallel (2S 3P variants).
Source:wikipedia