A solution of DNA molecules is put in a gel. Since each DNA molecule is charged negatively, it can be pulled through the gel with the help of an electric field. Small DNA molecules move faster through the gel compared to larger DNA molecules. The outcome is a series of "bands" and with each band it contains DNA molecules of a specific size. The bands which are furthest from the beginning of the gel has the smallest fragments of DNA. The bands that are closest to the beginning of the gel has the largest DNA fragments.
