Physical quantities,Fundamental quantities,Derived quantities,Principle of Homogeneity:

Physical quantities:
Simply, A quantity which can be measured is called physical quantities. For example we can measure the length of a pencil, so length is the physical quantity. Similarly velocity, angle, force, Pressure are some examples of physical quantities.
We cannot measure love, feelings, happiness, afraid etc. So these are not the physical quantities.
Physical quantities can be categorized into two types:
1. Fundamental quantities: The quantities which does not depend on any other quantity are called fundamental quantities. There are seven fundamental quantities discovered till date: All the fundamental quantities along with their units in SI system and their symbols are given below.

2. Derived quantities: The quantities which are are derived from the fundamental quantities are called derived quantities. For example: Force, speed, momentum etc.
What is dimension?
Let us know the basic things about dimension at first:
Dimension is the number of power to be raised to that physical quantity to represent that physical quantity. The dimension of Mass, length and time are represented as [M], [L] and [T] respectively.
Principle of Homogeneity:
In a simplest term, It states that “The dimension of a fundamental quantity of a left hand side must be equal to the dimensions on the right hand side of that equation.”
Example: The formula V = u + at is correct because the dimension of V is equal to the dimension of u + at.