Polymerase Chain Reaction (PCR) is a method to amplify a specific segment of DNA using primers and DNA polymerase. It involves repeated cycles of heating and cooling DNA to denature and renature it around the primers, allowing the polymerase to synthesize new strands. This amplification process produces millions of copies of the target DNA segment. The amplified DNA can then be analyzed by gel electrophoresis to identify the DNA of interest based on its molecular weight.