Karyotypes are images of chromosomes to display their banding patterns. When a nucleus is in during metaphase of mitosis, its chromosomes are condensed and the banding of the chromosomes can be visualized when certain dyes (e.g. Giemsa dye) are added to the chromosomes. There are several classical methods available to visualize the banding pattern as well as a more genomic one called chromosomal painting.
For those of us who are unaccustomed to seeing real chromosomes, often they are drawn in a cartoon fashion called an ideogram. Below is an ideogram of the X chromosome. The short arm of any chromosome is called the "p" arm which stands for the French word for small - petite. The long arm is called the "q" arm. Many years ago, histologist numbered the bands for each arm so we can refer to particular bands as genomic locations and everyone will be looking at the same band. The two telomeres are refered to as "ter" for termini. (see Chapter 10) You can follow the links below the image to learn more about karyotypes and chromosomal painting.