Weight
In modern scientific usage, weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a "force" that results from the action of gravity on matter: it measures how strongly the force of gravity pulls on that matter. However, in most practical everyday situations the word "weight" is used when, strictly, "mass" is meant. For example, most people would say that an object "weighs one kilogram", even though the kilogram is a unit of 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.