Explain what a methodless interface in a programming language is and how it is used.

In Go, an interface without methods is called an empty interface (interface{}). It contains no methods, so any type automatically implements this interface. This allows using the empty interface as a universal container for values of any type.

Example usage:

func printValue(v interface{}) {
    fmt.Println(v)
}

printValue(10)          // int
printValue("hello")   // string
printValue(true)       // bool

The empty interface is often used when working with data of unknown type, for example, in functions that accept arguments of any type, or when working with collections containing different types.