PCR (Polymerase Chain Reaction) amplification is a fundamental technique used in molecular biology to exponentially replicate specific segments of DNA. It revolutionized genetic research by enabling the rapid production of billions of copies of a targeted DNA sequence from a minute starting material.

The process involves several key steps:
1. **Denaturation**: The DNA sample, containing the target sequence, is heated to around 95°C, causing the double-stranded DNA to separate into two single strands.

2. **Annealing**: The reaction is cooled to a temperature typically between 50-65°C. Short DNA sequences called primers, which are designed to bind to specific regions flanking the target sequence, anneal or bind to their complementary sequences on the single-stranded DNA.

3. **Extension**: The temperature is raised to about 72°C, which is optimal for DNA polymerase activity. DNA polymerase, an enzyme, extends the primers by synthesizing new DNA strands complementary to the template DNA.

These three steps are repeated in cycles (usually 20-40 cycles), each cycle doubling the amount of DNA, resulting in an exponential amplification of the target DNA sequence. The final product is a large amount of DNA identical to the original target sequence, which can then be used for various applications in research, diagnostics, forensic analysis, and more.

PCR amplification is highly precise, sensitive, and has numerous applications, including genetic testing, sequencing, cloning, and detecting genetic mutations or pathogens.