A chromosome is just a compact store of DNA. A chromosome is simply a lot of DNA strands folded and compacted together. This compacting is done in a certain way. The Chemical bases in the DNA are held in place by The Double Helix. The Double Helix continues to wrap itself around proteins. They continue to wrap around several protein molecules and into an even bigger compact set which we call Chromosome.

Chromosomes are all contained in the nucleus of the cell. 

The number of Chromosomes in a cell depends on what cell it is. Chromosomes in a tiny goldfish may be a lot less than that of a human. Humans have 46 chromosomes in each of the cells of our organs. These are organized into two sets of 23 chromosomes.

Each human gets 23 chromosomes from their mom, and 23 chromosomes from their dad. This is why almost everyone has some traits they got from their parents.

By looking at the chromosomes in the cell, we can tell the gender of an unborn baby. Males have XY chromosomes and females have XX chromosomes.

These are called Sex Chromosomes.