Parents are people who have children. The word comes from the intensifier "older". It comes from the adjective "old". The word actually only exists as a plural. If you mean father or mother individually, you say parent. Some experts say parent for short.
People can be parents in different ways. They are the biological or natural parents of a child if they fathered the child. So biological parentage is about procreation and kinship. Children get their genes from their parents, the genetic material. That is why they sometimes look like their parents. For example, children may have inherited height, hair colour and so on from their parents, but also hereditary diseases.
Parenthood also exists in the field of law. For the state and the courts, it is important who is considered the parent of a child. Parents have rights: for example, they can decide which school the child attends and how the child is to be brought up. In most cases, the natural parents are also the legal parents. However, a child can also be adopted. This means that parents have taken in a child, but they have not fathered it themselves.
However, being a parent also entails duties to really take care of the child. This is "social" parenthood. For the child, it is then not necessarily so important whether the parents are biological or legal parents.
Stepchildren still have a natural parent, for example the mother. If the mother remarries, then this man is the stepfather for the child. It can also be the other way round: a child has its biological father and a stepmother.
Animals are also parents. In many animal species, however, the parents do not take care of their children: for example, they lay eggs and leave them. Or only one parent raises the young. Some animals do this together, for example wolves, some species of monkeys and some rodents.