This picture shows a family tree. The squares represent males in the family, while the circles represent females. Each individual has two copies of each gene - one set that is inherited from the mother and the other from the father.
With genes that are autosomal recessive, a person must have inherited two disease genes in order to get the disease - one from the mother and the other from the father. A person who has only one disease gene and one normal gene is called a carrier and does not have disease.
If two individuals who are carriers have a child, for each pregnancy there is a 25% chance of the child inheriting both disease genes. That individual may go onto have disease in the future.