Constants are variables that can'ts or can change?

Constant : these refers to values which do not change. they have the same value throughout the process. Like "1" is a constant value it will never change 1 will always remain 1. i.e.1=1

Varaibles= these refers to those quantities or values which change.for eg. if in a mathematical equation we have "X" variable. Now "X" can have number of values X =2 or X= 3 or X=10000 so they are called variables because their values change.