# Introduction

A **VARIO Cloud App** is an external web application that you build and host yourself. It is integrated into VARIO-Cloud in three ways:

* **UI integration**: VARIO Cloud embeds your App inside an iframe at defined integration points (for example, as a navigation entry or dialog). To the end user, the App appears as part of the ERP UI.
* **Data integration via REST API**: Your App talks to the VARIO Cloud backend using the public REST API (secured with OAuth2) to read and update ERP data.
* **Webhooks**: You can send and receive Events triggered by the Cloud App or via Webhooks

The App does **not** run inside VARIO Cloud itself. Instead, it is a self-hosted service that connects to VARIO Cloud through iframe-based UI integration and the REST API.

### App types: private vs public

VARIO Cloud supports **private Apps** and **public Apps**.

#### Private Apps

Private Apps are built for a single customer/organization.

* Any customer on the **Enterprise plan** can develop and add private Apps.
* Private Apps are not listed in the App Store.

#### Public Apps (App-Store)

Public Apps are available to all customers via the **App Store**.

* To develop a public App, you must contact us.
* You must sign an **App Store contract**.
* Before listing, the App goes through a **review process**.