// You can change the variable name and the value that i filled in. (witch is variable)
var variable = 47; // You can make this a string, a number, a boleean, an array and a object, but var is globally defined.
let variable = "a string" // As you can see i put a string and you can test it, it works. let is block scoped if you asked.
const variable = true // const is for if you want a variable not to change. So like pi if you made that a const or a variable (look at following example)
const pi = 3.14159265358979323846 // So now if you wish to add pi to calculate something you just type: "pi"