Letter Of Undertakings For Car What Is This Component Of A Letter Called?

What is this component of a letter called? - letter of undertakings for car

I know that opening a letter (Dear Mr. Man) is called a 'hello', but I can not think of the name) for the observation of the closing (Sincerely. I have to really remember what it is called. 10 points for the first person to answer correctly. Please! And thank you! :)