It's easy to understand why multiple bands would be present in the lanes containing DNA that has been cut with restriction enzymes, but why do you think there are several bands present in the lanes containing undigested (uncut) pGLO DNA? What do these bands represent?

These bands represent different confirmation of DNA

Explanation:

pGLO DNA is a plasmid DNA that is used as a vector for genetic engineering. Plasmid DNA is found in supercoiled confirmation in vivo. The double helix forms extra twists to easily fit inside the cells. During isolation of plasmid from the cell, nicks can be introduced in the DNA due to harsh isolating methods or contamination by nuclease. As a result the supercoiled confirmation is changed into circular confirmation. It is bulkier than the supercoiled form and travels more slowly. When both DNA stands get cut at the same place, the DNA gets liner confirmation. In the end, supercoiled DNA runs the fastest on gel followed by linear DNA and then the circular DNA.