A more thorough explanation:

Definition: A person who takes dictation or acts as a scribe or secretary.

Example 1: The author hired an amanuensis to transcribe her handwritten notes into a digital format.

Example 2: The CEO dictated a memo to his amanuensis, who then typed it up and sent it to all employees.

These examples show how an amanuensis is someone who takes dictation or writes down information on behalf of someone else. In the first example, the author needs help transcribing her notes, so she hires an amanuensis to do it for her. In the second example, the CEO needs to communicate with his employees, but he doesn't have time to type up a memo himself, so he dictates it to his amanuensis.