# Application users

Use these operations to install or uninstall apps from the Rebilly App Store to your Rebilly account, and to manage application instances.
An application user is a person or organization that uses an app that is installed from the Rebilly App Store.
For more information, see [Install or uninstall an app](https://www.rebilly.com/docs/dev-docs/install-an-app/).

## Retrieve an application instance

 - [GET /application-instances/{applicationId}](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/getapplicationinstance.md): Retrieves a list of application instances.
You may sort applications by: , , , ,
and .

## Upsert an application instance

 - [PUT /application-instances/{applicationId}](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/putapplicationinstance.md): Creates or updates (upserts) an application instance.

## Delete application instance

 - [DELETE /application-instances/{applicationId}](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/deleteapplicationinstance.md): Deletes an application instance with a specific ID.

## Retrieve an application instance configuration

 - [GET /application-instances/{applicationId}/configuration](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/getapplicationinstanceconfiguration.md): Retrieves the configuration of an installed application with a specified ID.

## Upsert an application instance configuration

 - [PUT /application-instances/{applicationId}/configuration](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/putapplicationinstanceconfiguration.md): Creates or updates (upserts) an application instance configuration.

## Retrieve applications

 - [GET /applications](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/getapplicationcollection.md): Retrieves a list of all applications.
You may sort applications by: , , , ,
and .

## Retrieve application

 - [GET /applications/{id}](https://www.rebilly.com/static/_spec/catalog/all-3.0/application-users/getapplication.md): Retrieves an application with a specified ID.