What does it mean if i have heterozygous dna?

I did a biology lab and I wasn't really listening but now I want to know the lab means. What's the difference between Heterozygous, zygous Positive, and zygous Negative DNA. The lab was to sc cheek cells and then do all these other steps until we load it into a gel box where we put electrical charges to see which DNA would move. Mine move which apparently means I have Heterozygous DNA. On the board the teacher had a column of all the counted students with zygous Positive, zygous Negative, and Heterozygous. Most were zygous Negative, fewer people were zygous Positive, and only two people in two periods were Heterozygous. What does it mean? I have heard of these kinds of alleles, but isn't DNA a little broad??