This is an oxidation-reduction (redox) reaction:
2 Mn0 - 14 e- → 2 MnVII (oxidation)
14 HI + 14 e- → 14 H0 (reduction)
Mn is a reducing agent, HBr is an oxidizing agent.
Reactants:

, Bromane
, Hydronium bromide
, Aqueous hydrogen bromide 
; Colorless gas with a sharp, irritating odor. [Note: Shipped as a liquefied compressed gas. Often used in an aqueous solution.] 
Products: