//js seletech var x = 3; //var can be re-assigned or re-declared var x = 4; x=5; let a = 10; a = 20; //let can be reassinged but not re-declared. const PI = 22/7; //can't reasssing or re-declare /* don't use var use let or const use const morethan let"+ use let when you need to reassign */