directus/docs/concepts/platform-overview.md

# Platform Overview

> The Directus platform is primarily comprised of an API and App, working in concert to "mirror" the schema and content
> of your SQL database.

## Database Mirroring

Instead of using a predefined "one-size-fits-all" data model to store your content, Directus "mirrors" your actual SQL
database in real-time. The principle is akin to a database client (eg: _phpMyAdmin_), but includes far more advanced
tools, and is safe and intuitive enough for non-technical users. This approach has many unique advantages:

- A custom SQL database schema, tailored to your exact requirements
- Significant performance improvements through optimizations and indexing
- Complete transparency, portability, and security for your data
- Direct database access and the full power of raw/complex SQL queries
- Allows importing existing databases, unaltered and without any migrations

## Directus API

The Directus API uses _Database Mirroring_ to dynamically generate REST endpoints and a GraphQL schema based on the
connected database's architecture. It is written in [Node.js](https://nodejs.org) and uses database abstraction to
support most [SQL database vendors](/guides/installation#databases).

### Relevant Docs

- [API Reference](/reference/api/introduction)
- [API Custom Endpoints](/concepts/api-extensions)

## Directus App

The Directus App is decoupled from, and powered by, the Directus API. It provides a way for both technical admins and
non-technical users to view and manage content of the connected database. It is written in [Vue.js](https://vuejs.org)
v3, is completely modular, and is highly customizable.

### Relevant Docs

- [App Overview](/concepts/app-overview)
- [App Extensions](/concepts/app-extensions)

## Projects & Environments

A Project is a complete instance of Directus. Each project primarily represents a database, but also includes a
configuration file and any related asset storage. This modular approach means you can also create different environments
(eg: Dev, Staging, Prod) by simply creating additional project instances.

<!-- ::: tip Migrating Environments
Directus includes [Export](#), [Import](#), [Backup](#), and [Restore](#) features to assist with custom migration workflows between environments. 
You can also roll your own process by copying the database and assets between environments, either manually or via an automated script.

@TODO Reference Schema Revisions
::: -->

## Collections

A Collection is a grouping of similar Items. Each collection represents a table in your database. Directus automatically
uses a built-in [title formatter](/concepts/app-extensions) to display your database table names prettified, and you can
use [translations](/concepts/data-model) to completely rename them if needed.

<!-- prettier-ignore-start -->
::: tip Usage
Collections can be organized in any way that is appropriate for your project. You can
architect them platform-specific (eg: _pages_ of a website), or in a more platform-agnostic way (eg:
raw _customers_ of your business). While there's no right or wrong way to structure your data-model,
we recommend keeping your data as agnostic as possible so it is easier to repurpose in the future.
In short, **learn to see your data as its own asset — not only through the lens of your immediate
project needs**.
:::
<!-- prettier-ignore-end -->

### Relevant Guides

- [Creating a Collection](/guides/collections#creating-a-collection)
- [Deleting a Collection](/guides/collections#deleting-a-collection)

## Presets

Presets store the exact state of a [collection detail](/concepts/app-overview) page. These are used to set layout
defaults for a user, or to define bookmarks that can be used to quickly recall specific datasets.

### Relevant Guides

- [Creating a Preset](/guides/presets#creating-a-preset)
- [Deleting a Preset](/guides/presets#deleting-a-preset)

## Fields

A Field is a specific type of value within a Collection. Each field represents a database column. Directus automatically
uses a built-in [title formatter](/concepts/app-extensions#title-formatter) to display your database column names
prettified, and you can use [translations](/guides/fields) to completely rename them if needed.

Each field also mirrors other characteristics from the column, including its `type`, `default`, `length`, `allow_null`,
etc.

<!-- prettier-ignore-start -->
::: tip Usage
You might have `title`, `body`, `author`, and `date_published` fields within an
`articles` collection.
:::
<!-- prettier-ignore-end -->

<!-- prettier-ignore-start -->
::: tip Aliases
Not all fields in Directus map directly to an actual database column within their
table. Some relational fields, like One-to-Many (O2M) and Many-to-Many (M2M), represent data that is
stored in different tables. Other fields are only for presentation and don't save data at all, such
as a divider. These are called "alias" fields.
:::
<!-- prettier-ignore-end -->

<!-- prettier-ignore-start -->
::: tip Relational Fields
Fields that reference other items (in the same collection or different)
are called relational fields. Linking or connecting data relationally is an immensely powerful
feature of relational databases and SQL queries.
:::
<!-- prettier-ignore-end -->

### Relevant Guides

- [Creating a Standard Field](/guides/field-types/standard-field)
- [Creating a Presentation Field](/guides/field-types/presentation-field)
- [Creating a Many-to-One Field](/guides/field-types/many-to-one-field)
- [Creating a One-to-Many Field](/guides/field-types/one-to-many-field)
- [Creating a Many-to-Many Field](/guides/field-types/many-to-many-field)
- [Creating a Many-to-Any Field](/guides/field-types/many-to-any-field)
- [Creating Translated Fields](/guides/field-types/translated-fields)
- [Duplicating Fields](/guides/fields#duplicating-a-field)
- [Adjusting Field Layout](/guides/fields#adjusting-field-layout)
- [Deleting Fields](/guides/fields#deleting-a-field)

## Types

Directus has built-in database abstraction for managing all SQL database vendors. However, each of those vendors has a
different list of supported column datatypes. To standardize all of these differences, Directus has a single superset of
types that each map to the more specific vendor ones.

- String
- Text
- Boolean
- Integer
- Big Integer
- Float
- Decimal
- Timestamp
- DateTime
- Date
- Time
- JSON
- CSV
- UUID

@TODO confirm

## Items

An Item is an object containing the field values within a Collection. Each item represents a database record. Similar to
a "row" within a spreadsheet.

### Relevant Guides

- [Creating an Item](/guides/items#creating-an-item)
- [Archiving an Item](/guides/items#archiving-an-item)
- [Reordering Items](/guides/items#reordering-items)
- [Deleting an Item](/guides/items#deleting-an-item)