So as you recall, DNA is the storehouse of information in the cell. DNA is organized into chromosomes and all of the DNA in the cell is referred to as the genome.
DNA is a linear molecule; it's kind of like a string, kind of like our light strings that we're talking about. The difference here though, between our tangled Christmas tree lights and our DNA, is that we have three billion bases! That's a lot of string that's all got to be wadded up inside of the nucleus. So we've got to figure out a way to efficiently pack that DNA into the nucleus, one, so that it just fits inside of the nucleus, and two, so that we can actually access the information that DNA has to offer.