Explain Enums in a Relatable Way

Enun is a type of variable, like Int or bool.

Each type of variable can contains only specific values. For example an Int can contains only numbers, a boolean can contain only true or false. But what about if you need a variable that can contain only your custom list of values? For example you need a variable to store the grade at your school, that's is only "a", "b", "c", "d", "e", "f" ? of course you can use an int variable for this, or even a string, but wouldn't be more explicit if your variable could only have those values? yes, it would :) and in facts is possible

enum Grade {
    case a
    case b
    case c
    case d
    case e
    case f
}

var enumFinalGrade: Grade = Grade.a //<- this is awesome
var stringFinalGrade: String = "a" // <- this is error prone
var stringFinalGrade = "foobar" // <- this is valid for the compiler, but doesn't make any sense

In swift enums are more complicated then this, because you can have associated values with each value, but go step by step. Grasp the basic enum idea, then move to the more advanced usages.