Variable declaration

we use three identifiers in java script var,let,Const.
var means variable. By using var we can declare redeclare and reinitiate values for a variable .
example: var x =5
var x=6
x =7
if we use let and declare a variable then we can declare it once and we cant redeclare it again but we can reinitiate it again.
example: let x =5
x=6
if we use const we can declare the variable only once we cant redeclare and reinitiate it again.we declare the data also while declaring the const.
const m=5.