Chromosomes contain the hereditary information of an organism. They are composed of DNA and can be found in the nucleus of the cell. Living things have a specific number of chromosomes in each species. For example, humans have 46 chromosomes. During interphase(resting stage), the chromosomes are replicated. This is necessary before the cell enters the cell cycle and carries out mitosis. By copying the chromosomes, each daughter cell gets a full complement of the DNA it will need to carry out its life processes. Chromosomes are also found in sex cells or gametes--sperm and egg cells. During meiosis, diploid teste and ovary cells produce gametes which are haploid. When fertilization occurs, the diploid condition is restored in the zygote once again. Chromosomes from each parent combine to form the genotype of the resultiing offspring. Chromosomes contain distinct segments called genes. Genes are necessary to provide the instructions to produce proteins that the cell needs for its survival.
Well, they are large molecules of your DNA and without them your body couldn't have been created.
Consider a brick house. Without the chromosomes, you'd just have all the raw materials but no construction started.