A murder is considered as the most grieve and severe criminal act in which one person kills the other intentionally. He kills someone with planning and it is also known as target killing.
While in the case of manslaughter, a person kills another person without having intention of killing. A person gets killed either as a result of an unintentional or accidental act of the killer.
In a murder, a killer has clear intention of killing another person and he plans about how to kill the other person. Usually the reasons are either enmity or other rivalry.
On the other hand, manslaughter is entirely different in which a person does not want to kill someone but he ends up doing so as a result of accident or unintentional act. For example, he is trying to clean a gun which is loaded and by chance he pushes the trigger and someone nearby get shot.
The punishment of a murder is different from the punishment of manslaughter because the nature of both crimes differs greatly and many courts of law all over the world determine punishment which is not equal in both cases.
In U.S.A, the punishment of a murder is life imprisonment or death because the act is being done intentionally and with complete planning.
On the contrary, the punishment for manslaughter is usually 20 to 40 years of imprisonment. In U.S.A usually a culprit of manslaughter is imprisoned for 20 years. It is less than a murder because the killer had no intention of killing someone.