Final answer:
The term 'enclosure' is used to indicate additional items included with a letter, listed at the end of the letter below the sender's typed name.
Step-by-step explanation:
The notation used to indicate something that is included within the same package as a letter is called an enclosure. When you are sending a letter and wish to note that other items are included in the envelope, you should list these items after the word Enclosures, which will be placed one line below your typed name, typically at the end of the letter.
An enclosure can be anything from a resume to a writing sample or any other document you wish to send along with your letter.