The PCR process can generally be divided into three stages and visualized on a graph.
The first stage is the exponential amplification where the doubling of the DNA product will occur with each cycle. At this stage there is an excess of reagents and a limited number of templates, so product renaturation does not compete with primer binding.
The second stage is the leveling off stage in which the reaction slows down due to the loss of activity of the DNA polymerase and the consumption of reagents. At this point the product renaturation is competing with primer binding.
The third stage is the plateau stage in which no more products accumulate due to a complete exhaustion of dNTPs and reagents.