In terms of detection, there are two ways of detecting PCR products-one is the conventional method that has been used since the beginning of PCR, that is to analyze the PCR reactions using agarose gel electrophoresis. Since this is done at the end of a PCR run, this type of PCR is called end-point PCR
A newer type is the real-time PCR, in which a fluorescent probe is used in PCR reactions, and a fluorescent reading is made in each cycle of amplification. As amplification takes place, the fluorescence will be increasing to the extent that it is significant. Typically, as soon as amplification reaches a threshold, it will be detected. Therefore, this type of PCR is referred to as real-time PCR.
In general a real-time PCR reaction in which DNA template concentration is high is amplified in shorter time, or fewer cycles than that in which DNA template concentration is low. This has become the basis of quantifying DNA template concentration using real-time PCR. This real-time PCR subtype is often referred to as quantitative PCR or qPCR.