Is it mandatory to use ActiveForm to create forms in YII2?

Question

Yii

Hello.
Now I am transferring one project to YII2. Haven't worked with him before.
And here a question arose when creating a login form.
In the documentation, ActiveForm is used to create a login form.
Is this the only way to create a form in Yii2 so that the validation rules work correctly?

public function rules()
{
    return [
        // the name, email, subject and body attributes are required
        [['name', 'email', 'subject', 'body'], 'required'],

        // the email attribute should be a valid email address
        ['email', 'email'],
    ];
}

UPD: See the answer in the comments

Answer 1

It is important to understand that the framework - simplifies the work. If you want - no one forbids you to mark up your form, add JS validation (using any libraries), process it on the server, etc. Question: what is it for?