Mass
In everyday usage, mass and "weight" are often used interchangeably. For instance, a person's weight may be stated as 75 kg. In a constant gravitational field, the weight of an object is proportional to its mass, and it is unproblematic to use the same unit for both concepts. But because of slight differences in the strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets. Conceptually, "mass" (measured in kilograms) refers to an intrinsic property of an object, whereas "weight" (measured in newtons) measures an object's resistance to deviating from its natural course of free fall, which can be influenced by the nearby gravitational field. No matter how strong the gravitational field, objects in free fall are weightless, though they still have mass.
Jupiter mass
The mass of Jupiter is derived from the measured value called the Jovian mass parameter, which is denoted with "GM". The mass of Jupiter is calculated by dividing "GM" by the constant "G". For celestial bodies such as Jupiter, Earth and the Sun, the value of the "GM" product is known to many orders of magnitude more precisely than either factor independently. The limited precision available for "G" limits the uncertainty of the derived mass. For this reason, astronomers often prefer to refer to the gravitational parameter, rather than the explicit mass. The "GM" products are used when computing the ratio of Jupiter mass relative to other objects.