Genetics is the science of explaining inheritance. Organisms can transfer characteristics to their offspring. These characteristics can skip a generation or even two, depending on the inheritance shape, but they are always transferred from parent to child. All of the hereditary characteristics together is called the genotype.
When breeding two animals you want to know what colors their offspring will be. With genetics you can calculate it but you need to know a lot about the parents first. Depending on the color of the parents can you see which genes ensure that color. You can cross these genes in a calculation. That is looking which allele is given on by the parents to their offspring. And what parents pass on to their offspring: that is inheritance.
DNA, alleles and genotype
A DNA-strand is composed of two very long wires and between those two wires, hang smaller wires called genes. On these genes is written all information which a hedgehog has received from his parents. A gene is composed of two parts called alleles: one part he got from his mother and the other part he has inherited from his father. Each parent gives one half of such a gene to his/her children. But which part that is depends on the form of inheritance. All of these alleles taken together in a DNA-strand, define the color and the pattern of a hedgehog. This is called the genotype.