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. This is just one step reaction.
Reduction of nitrobenzene to aniline is oxidation reducing reaction. (redox)
Nitrobenzene is reduced to aniline salt by Sn / concentrated HCl. Instead of Tin zinc or iron 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.
Both nitrobenzene and aniline are liquids at room temperature.