Why are 2 primers needed for PCR?

Two primers, forward primer and reverse primer, are used in each PCR reaction, which are designed to flank the target region for amplification. Two complementary single strands of DNA are released during denaturation. The forward primer binds to the template DNA, while the reverse primer binds to the other complementary strand, both of which are amplified in PCR reaction. If only one primer is used, the process is called “asymmetric PCR”. Only one strand of the double-stranded DNA will be amplified, and only one new copy is synthesized per cycle, which is unable to achieve exponential amplification.