Answer : In the redox reaction,
Nitrogen element is oxidized and sulfur element is reduced.
act as reducing agent and 
act as an oxidizing agent.
Explanation :
Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.
Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.
Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.
Reducing agent : It is defined as the agent which helps the other substance to reduce and itself gets oxidized. Thus, it will undergo oxidation reaction.
Oxidizing agent : It is defined as the agent which helps the other substance to oxidize and itself gets reduced. Thus, it will undergo reduction reaction.
The given chemical reaction is,
This reaction is a redox reaction in which nitrogen shows oxidation reaction because the oxidation state of 'N' changes from (+4) to (+5) and sulfur shows reduction reaction because the oxidation state of 'S' changes from (+6) to (+4).
In the redox reaction act as reducing agent and act as an oxidizing agent.
