The reaction is a displacement (halogen displacement) reaction , which is also a redox reaction.

What happens in this reaction

  • Chlorine (Cl2Cl_2Cl2​) is more reactive than bromine, so it displaces bromide ions from sodium bromide solution.
  • The ionic equation is: Cl2+2Br−→2Cl−+Br2Cl_2+2Br^-\rightarrow 2Cl^-+Br_2Cl2​+2Br−→2Cl−+Br2​. This shows bromide ions being oxidised to bromine and chlorine being reduced to chloride.
  • The orange/brown colour comes from bromine (Br2Br_2Br2​) formed in solution.

Type of reaction (exam-style wording)

In exam or textbook language, this process is typically described as:

  • A displacement reaction (more reactive chlorine displaces bromine from sodium bromide).
  • Also a redox reaction , because electron transfer occurs between chlorine and bromide ions.

So the best short answer to “what type of reaction has taken place?” is: a halogen displacement reaction (a type of redox reaction).