Explaind the role of DNA-dependent RNA polymerase in transcription

RNA polymerase catalyzes RNA synthesis. To transcribe a gene ,RNA polymerase proceeds through a series of well-defined steps, which are grouped into three phases: initiation, elongation, termination.
1.Intitiation: RNA polymerase binds with the promoter region of the DNA. The promoter polymerase complex undergoes structural changes required for transcription.
2.Elongation: During elongation, RNA polymerase unwinds the DNA in front and re-anneals it behind ; it dissociates the growing RNA chain from the template as it moves along. It also performs proofreading function.
3.Termination: Once the polymerase has transcribed the length of the gene, it stops and releases the RNA product.