The phrase refers to textual attachments extracted from electronic mail messages. For example, a document created in a word processor might be included within the body of an email, rather than as a separate file. This method embeds the content directly into the message, viewable without opening an external file.
This practice offered advantages in situations where recipients faced limitations in software compatibility or bandwidth. It also provided a means of ensuring immediate visibility of critical data, reducing the need for additional steps to access information. Historically, it served as a workaround when dealing with diverse operating systems and email client capabilities.