What does the second argument of the function represent when returning ZeroValue in certain programming languages?

In many programming languages, including Go, a function can return multiple values, such as a result and an error.

In the context of Go, when a function returns ZeroValue (the zero value of a type) as the first argument, the second argument is often used to convey information about an error or execution status.

For example, a function might have the signature:

func GetUser(id int) (User, error)

If the user is not found, the function returns User{} — the zero value of the User struct — and an error describing the problem:

return User{}, errors.New("user not found")

Thus, the second argument serves to pass additional information about the operation's result, most often an error, allowing the calling code to handle the situation correctly.