Steamworks Documentation
An Application (or App) is the main representation of a product on Steam. An App generally has its own store page, it's own Community Hub, and is what appears in customers' libraries.

Each App is represented by a unique ID called an App ID - that you'll see referenced throughout this documentation and used with the Steamworks API and Steamworks Web API. Generally a single product will not span multiple Applications.

Creating Applications

New Applications can be created by any Administrator in your Steamworks partner group. Once the Steam Direct Fee for a new Application has been purchased or you have been granted an app credit, it can be redeemed by clicking "Create new app..." under "Create A New Application" on the Steamworks landing page.

Types of Applications

The following are the different types of applications that you can create on Steam.
You can set the type of your app on the General Application Settings section of the App Admin panel.
Game All games, including VR and non-VR titles, will be under this application type.
Software Products such as Audio Production, Design & Illustration, and Photo Editing will be under this application type.
DLC Downloadable Content (DLC) are additional content for your game that can be purchased or downloaded for free. They are normally used for soundtracks, artbooks, and extra in-game content. This application type will have a separate App ID from the base application but will be linked to it. Please see the Downloadable Content (DLC) documentation for more information.
Video, Series and Episode Products such as movies, TV shows, game videos and tutorials will be under these application types. More information can be found in the Steam Video section.
Demo Steam has the option to provide free demos for your customers so that they can try the game before purchasing. Demos are created through the main App and will appear as a button on the main game's store page. This application type will have a separate App ID from the base application but will be linked to it. Please see the Demos documentation for more information.

Additional aspects of Applications

The App itself is just one part of the overall content ecosystem on Steam. This section provides a high level overview of the different pieces that make up an application.
Bundles These are optional groups of packages that allow multiple packages to be bundled together and sold with a discount.
Packages A package is a collection of one or more applications and depots that can be sold via Steam or can be granted to users based on the activation of a Steam key. This can be thought of as an SKU or a license.
Depots A depot is a logical grouping of files which are all delivered to a customer as a single group.
Builds A build is the result of Uploading to Steam, it can contain 1 or more of your depots and is a representation of those depots at that point in time.
Branches (Betas) A branch, or beta, is a specific build that you have made available either publicly or privately. Once your title is live, the "Default" branch is the build that is delivered to customers. Additional builds can be listed under the beta tab or hidden using a password. Password-protected branches are not visible to any account without the password.

This can be visualized like this: