Transcription refers to the process of synthesizing RNA molecules from a DNA template. It is a key step in gene expression, where genetic information encoded in DNA is used to build RNA molecules. The process involves an enzyme called RNA polymerase, which binds to a specific region on the DNA called the promoter. The enzyme then unwinds and separates the DNA strands and starts adding RNA nucleotides that are complementary to the DNA template. This results in the formation of a single strand of RNA called messenger RNA (mRNA).

Options 1, 2, and 3 are incorrect because transcription does not involve the synthesis of lipids, proteins, or DNA itself. However, option 4 is correct as RNA is the synthesized product during transcription.