Transcription is the process of copying information from DNA to mRNA in three main stages: initiation, elongation, and termination. In initiation, the enzyme RNA polymerase binds to the promoter region of a gene, unwinding the DNA strand. Elongation involves RNA polymerase building the mRNA molecule using complementary bases to the unwound DNA. Termination occurs when RNA polymerase crosses a stop sequence, detaching the completed mRNA from the DNA.