What is the difference between `let` and `var` in swift?

Question

What is the difference between let and var in Apple\'s Swift language?

In my understanding, it is a compiled language but it does not check

Answer 1

let keyword defines a constant

let myNum = 7

so myNum can't be changed afterwards;

But var defines an ordinary variable.

The value of a constant doesn’t need to be known at compile time, but you must assign it a value exactly once.

You can use almost any character you like for constant and variable names, including Unicode characters;

e.g.

var x = 7 // here x is instantiated with 7 
x = 99 // now x is 99 it means it has been changed.

But if we take let then...

let x = 7 // here also x is instantiated with 7 
x = 99 // this will a compile time error