the positive control tests that all of your pcr reagents and the cycling are working properly. The negative control of water in place of dna tests that you have no contamination of pcr product that is amplifying and looking like all of your samples are amplifying

The main purpose of internal control is to ensure the accuracy and reliability of the results. Internal controls act as a reference to identify any unexpected amplification that may arise from contamination. It can also be used as a baseline comparison to evaluate the efficiency of the PCR reaction.

Internal controls help identify and prevent contamination issues. Contamination can lead to false-positive results, and internal controls help ensure that the detected signals are indeed from the target DNA and not from external sources.

Internal control expression in both negative and positive sample and by internal control we ensure the DNA was extracted very well and there is no contamination