What do you understand by the term ‘mass’? Name any one instrument used for weighing.

Hint: Weight and mass are both different terms mostly used together. We can’t mix both totally separate terms. Though both are related to each other such as weight and mass are directly proportional to each other. Weight is the measurement of force applied by a piece of mass. But in practical life we used to measure weight instead of mass by using different equipment.

Complete step by step solution:
Mass, in common words, is the amount of matter contained in a body. Mass is a physical quantity with S.I. unit \[kg/{\text{kilogram}}\] . It is a scalar quantity (i.e. remains the same on changing the direction). Mass can be termed with respect to several other factors.
In terms of acceleration, mass is the physical quantity that offers resistance to flow. It is directly proportional to force while inversely to acceleration. Body having higher mass offers large force and to the motion, a body with higher mass provides larger friction force or negative acceleration (i.e. retardation/resistance).
This is stated in Newton’s Second Law:
$F = ma$
Where, $F = {\text{Force}}$
$m = {\text{mass}}$
$a = {\text{acceleration}}$
It can also be stated as the pull it applies on different masses due to its gravity. Larger mass pulls smaller masses toward itself due to the gravitational field it generates.
$F = \dfrac{{G{m_1}{m_2}}}{{{r^2}}}$
Where, $F = {\text{Gravitational Force}}$
${m_1}{m_2} = {\text{larger mass and smaller mass}}$
$r = {\text{distance between both masses}}$
And mass is also defined in quantum physics as the difference of an object’s quantum frequency and wave number.
As in the present scenario we used to measure mass in terms of weight and are frequently interchanging both terms. Weight is the force applied by a mass.
There are several instruments used in day to day life to measure weight of body including:
Weighing scale and Balances.

Note: It is a frequent mistake of using weight instead of mass. Never mix up such quantities opposite in all fractions. Though both depend on each other, weight is a vector quantity while mass is a scalar quantity. S.I. unit of mass is \[kg/{\text{kilogram}}\] and C.G.S. unit is $g/gram$ . Mass never varies in vacuum or by changing direction as it is just total matter prevalent.