Nitrobenzene is reduced to get aniline in organic chemistry. Aniline is very important organic chemical in organic chemistry becuase it is used to produce more organic compounds.
Reduction of nitrobenzene to aniline is oxidation reducing reaction. (redox)
Nitrobenzene is reduced to aniline salt by Sn / concentrated HCl. Instead of Sn, Zn or Fe can be used too to reduce nitrobenze to aniline.
Aniline is taken from aniline salt by reacting it with NaOH. This is an weak acid and strong base reaction.