What is a document ?

About

A document is:

a text
that may be located
- in the content of a file,
- in the body of an HTTP request
- in a database
- in a string (memory)
- … and more
that has a particular structure (given by its mime for http or extension for a file, …)

Documents on the web (saved in a body request) have generally by nature a hierarchical nature (as opposed to tabular)

This is generally a HTML document but it can be also other type of document such as:

This document (file) can be rendered by the user agent (Generally a browser)

The term document in a file system is generally a file including its structure and format, e.g. fonts, colors, and images.

Database can store document in a field or as a row and offers function for document processing. See Database - Document Database

In natural language processing / full text search, a document is composed of word (term) known also as bag of word. See Natural Language - Document