What is difference between 'let' and 'var' declaration ?

constants are expressed with the ‘let’ keyword. So once assigned value can not be change, but assigned values using ‘var’ keyword can be change.

In terms of objective -c or compare with objective -c, ‘var’ is Mutable and ‘let’ is NonMutable.

let kMyConstant = 40
Or
let kMyConstant: Int = 40

var myString = “This is my string.”