Question

what is variable and constant

Answer 1

The value of a Variable changes.
But the value of a Constant never changes.

Ex
a is variable, the value of a may be 5,4,9,etc.
but 5 is constant and its value will be always 5.

Answer 2

Value of a variable can change

For Example :-

In one question

x = 2

Maybe in other question

x = 5 or other

The value of constant can't change,

For Example :-

5 is always equal to 5 only, 5 will never be equal to 10