Small improvements to docs/topics/db/models.txt

.. module:: django.db.models

A model is the single, definitive source of data about your data. It contains

the essential fields and behaviors of the data you're storing. Generally, each

model maps to a single database table.

A model is the single, definitive source of information about your data. It

contains the essential fields and behaviors of the data you're storing.

Generally, each model maps to a single database table.

The basics:

* The name of the table, ``myapp_person``, is automatically derived from

  some model metadata but can be overridden. See :ref:`table-names` for more

  details..

  details.

* An ``id`` field is added automatically, but this behavior can be

  overridden. See :ref:`automatic-primary-key-fields`.

* The database column type (e.g. ``INTEGER``, ``VARCHAR``).

* The default :doc:`widget </ref/forms/widgets>` to use when rendering a form

* The default HTML :doc:`widget </ref/forms/widgets>` to use when rendering a form

  field (e.g. ``<input type="text">``, ``<select>``).

* The minimal validation requirements, used in Django's admin and in

``id`` column.

Each model requires exactly one field to have :attr:`primary_key=True

<Field.primary_key>`.

<Field.primary_key>` (either explicitly declared or automatically added).

.. _verbose-field-names: