Biologically, a child (plural: children) is generally a human between the stages of birth and puberty. The legal definition of child generally refers to a minor, otherwise known as a person younger than the age of majority.
Child may also describe a relationship with a parent (such as sons and daughters of any age) or, metaphorically, an authority figure, or signify group membership in a clan, tribe, or religion; it can also signify being strongly affected by a specific time, place, or circumstance, as in "a child of nature" or "a child of the Sixties".
There are many social issues that affect children, such as childhood education, bullying, child poverty, dysfunctional families and in developing countries, hunger. Children can be raised by parents, in a foster care or similar supervised arrangement, guardians or partially raised in a day care center.
Source: Wikipedia, Link