Final answer:
Attachment notation is used when a document or file is physically attached or included with a letter or email, while enclosure notation is used when additional documents or files are included in the same envelope but not physically attached to the letter or email.
Step-by-step explanation:
The main difference between attachment notation and enclosure notation is the purpose for which they are used. Attachment notation is used when a document or file is physically attached or included with a letter or email. It is typically indicated by writing 'Attachment:' or 'Attached:' followed by a brief description of the attachment. On the other hand, enclosure notation is used when additional documents or files are included in the same envelope but not physically attached to the letter or email. It is typically indicated by writing 'Enclosure:' or 'Enclosed:' followed by a list of the enclosed documents or files.