What is the difference between a positive control and a negative control?

The positive control is set to determine the position of the band, if you are not sure of the location of the band, or there is a interference band similar in size to the band of interest, you can use a plasmid containing your gene of interest as the positive control, and use the plasmid instead of the template to react. The negative control mainly excludes false positives caused by some reagents or operations in the experiment, the template is not added to the reaction system, and other reagents are added normally. I generally do not set a control group when performing normal amplified PCR, and I set a negative control when performing colony PCR and other verification, and a positive control only when it is necessary to confirm the location of the target band.