A legal guardian takes over day-to-day decision making and control of the child from the natural guardian under a court order. A legal guardian, generally speaking, takes over the care and upbringing of the child, making all parenting decisions
This video may help you understand the divorce process in Maine. It applies specifically to divorces where the parties have mutual children. Most of this information also applies where unmarried couples need a court order determining their "parental rights and responsibilities." That process is much like getting a divorce, except that the parties are not married.