There are many different ways that surrogates can work. The most common way is for the surrogate to be implanted with the embryo of the intended parents. This is done through in vitro fertilization (IVF), where the egg and sperm are combined in a lab and then transferred to the surrogate's uterus. The surrogate then carries the baby to term and delivers him or her to the intended parents.
Other surrogates may carry a baby that is not related to them genetically. This can happen when someone donates their eggs or sperm, or when embryos are created from donor eggs and sperm and then implanted into the surrogate. Additionally, a gestational carrier is a type of surrogate who does not provide any genetic material for the baby she is carrying; instead, she simply acts as a host for the pregnancy.
The legal arrangements surrounding surrogacy can vary greatly from country to country, so it's important to do your research before entering into any agreements. In some cases, the surrogate may have no legal rights over the child she carries; in others, she may be considered the child's legal mother until he or she is handed over to the intended parents at birth. It's crucial that everyone involved understands their rights and responsibilities before moving forward with any type of surrogacy arrangement.