Mass and weight are related in that mass is an important factor in calculating weight, but they are not alike. Mass is the amount of material present in any object, while weight is the measurement of the force with which gravity acts upon the object.
The mass of an object is fixed, but weight varies with the change of gravitational pull. The mass of an object is the amount of material present in the object, meaning that an object has the same mass regardless of its location. Weight, however, is a force that is mathematically defined as weight = mass * gravitational pull.
Since Earth's gravity is roughly consistent throughout the planet, an object weighs roughly the same at all places on Earth, while the mass of that object is always exactly the same, regardless of planet. So, the mass of an object is constant, and the weight of an object depends on the gravitational pull. For example, the gravitational pull on the surface of the moon is roughly 1/6 of that on Earth. So, if an object is weighed on the Earth and the moon separately, the weight of that object on the moon would be approximately 1/6 of its weight on Earth. But since it's the same object, the mass of that object stays the same on Earth and on the moon.