What is the difference between Type Alias and Type Definition in Go?

Type alias:

type A = string

Type definition:

type A string

What is the difference between them? I can't understand from spec

type A = string creates an alias for string. Whenever you use A in your code, it works just like string. So for example, you can't define methods on it.

type A string defines a new type, which has the same representation as string. You can convert between an A and string at zero cost (because they are the same), but you can define methods on your new type, and reflection will know about the type A.

For example (on the playground)

package main

import (
    "fmt"
)

type A = string
type B string

func main() {
    var a A = "hello"
    var b B = "hello"
    fmt.Printf("a is %T\nb is %T\n", a, b)
}

Output:

a is string
b is main.B