qPCR is similar to regular PCR, but with each cycle the qPCR machine quantifies the amount of fluorescence that is generated by a probe that attaches to a specific sequence of DNA. The technique specializes in providing an absolute count of the number of copies of a sequence initially in a solution and can be made so that it is species specific. It is used mostly to detect the presence (or suggest the absence) of a single species and/or provide an absolute abundance of its DNA.