Answer 1

Immutable objects can't be changed after it is created. It means you can't modify their values/elements

For example strings in JS

var str = "David" // declaration

str[0] = 'A' //. Wrong because strings are immutable

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Mutable objects are those that can be change later

For example arrays

var arr = [ 1, 2, 3]

arr[0] = 1000 //. valid