Being a carrier means having a pathogenic variant in one of the two copies of a gene associated with a recessive hereditary condition. This usually causes no symptoms, but you can pass the variant on to your children.
For an autosomal recessive condition, if your partner is also a carrier of a pathogenic variant in the same gene, each pregnancy has a 25% chance that the baby will inherit a variant from each parent and develop the condition, a 50% chance that the baby will be a carrier and a 25% chance that the baby will inherit neither variant. For X-linked recessive conditions, a female carrier has a 50% chance of passing on the variant in each pregnancy: a son who inherits it may develop the condition, while a daughter who inherits it will usually be a carrier. In both cases, it is advisable to consult a genetic counselling specialist before planning a pregnancy.