When you define const you can initially assign value to it as constant value. But later on in code you can't change it. Meaning if you try to assign something later to it it won't allow you.
const a = 3;
a = 4 // this won't work
but there is a catch you can still change value of const variables if they are objects or arrays, const means that you can't change type of variable.
const a = {
b: 'test 1'
};
a.b = 'test 2' // this will work
:) hope this will help you.