Autosomal is a word for the chromosomes of the body that are not the sex-determining chromosomes. Humans have 46 chromosomes: 22 pairs of autosomes and one pair of sex chromosomes.
To be autosomal recessive means that two copies of a gene must be present for a trait to be passed down in families. If one gene of the pair is defective, the person is considered a carrier. If both parents are carriers of an autosomal recessive gene, there is a 1 in 4 chance of developing the disease and a 50% chance of being a carrier.
To be autosomal dominant means that only one gene is necessary in order to inherit a disease or condition. There is a 50% chance of passing the condition to offspring.