Physical quantities are the things which have a definite measurable magnitude, which could be expressed in certain numbers. The important fact is that they could be measured through certain physical systems. The most important examples of physical quantities are length, mass, time, electric current, and intensity of light etc. Physical quantities are further subdivided into categories of direct/fundamental and indirect/non fundamental physical quantities the direct/fundamental physical quantities are those physical quantities which could be directly measured and their magnitude could be directly expressed in numbers with certain units.
The non fundamental physical quantities are those quantities which could be quantified or expressed in numbers through the units of fundamental physical quantities. The units of these physical quantities are also called derived units. And the units of fundamental physical quantities are called fundamental unit.
Length is a fundamental physical quantity which is used to express the magnitude of the distance covered or to be covered by anything. Its units are different in different system but in system international of units its units are meters. Mass is a measure of quantity of matter in a body it describes that how heavy or light a body could be its units are Kilograms in system international. Similarly time is a measure of duration between any events and its units are seconds.
The foundation of Physics rests upon physical quantities in terms of which the laws of Physics are expressed. Therefore, these quantities have to be measured accurately. Among these are mass, length, time, velocity, force, density, temperature, electric current and numerous others.
Physical quantities are often divided into two categories: base quantities and derived quantities. Derived quantities are those whose definitions are based on other physical quantities. Velocity, acceleration and force etc. are usually viewed as derived quantities. Base quantities are not defined in terms of other physical quantities. The base quantities are the minimum number of those physical quantities in terms of which other physical quantities can be defined.
Typical examples of base quantities are length, mass and time.
The measurement of a base quantity involves two steps: First, the choice of a standard, and second, the establishment of a procedure for comparing the quantity to be measured with the standard so that a number and a unit are determined as the measure of that quantity.
An ideal standard has two principal characteristics: it is accessible and it is invariable. These two requirements are often incompatible and a compromise has to be made between them. It's all about physical quantities.
There are some characterstics of every material object. These are to be measured to specify them e.g to specify the characterstic of a brick its length and mass are to be measured . Such characterstics are called physical quantites.