Docs/init overview (#329)

* 🔥 docs rm example pages

* 📝 docs init overview

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docs/overview.md

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 # Overview
+
+The reference architecture of it@M (further referred to as "RefArch") provides a frame for developing web applications and integration components.
+It's based on [Spring](https://spring.io/) as backend framework and [Vue.js](https://vuejs.org/) as frontend framework. [Apache Camel](https://camel.apache.org/) is used as integration framework.
+
+This website contains documentation for the general topics about the reference architecture, as well as content about generic and ready-to-use components.
+Additionally, there is [documentation for repository templates](https://refarch-templates.oss.muenchen.de), which is especially relevant when developing own applications with the RefArch.
+
+The following sections further describe the architecture and its involved components.
+
+## Architecture
+
+The RefArch is a microservice-based architecture where each service can be scaled and developed independently.
+Following up is a description of the different components and a visualization of the connections between them.
+
+Most applications consist of an API gateway, a frontend (served by a webserver) and a backend component.
+Besides that there can be cases where modular frontends through web components, multiple frontends or multiple backends are desired.
+
+```mermaid
+flowchart LR
+    u([Users])
+    g[API-Gateway]
+    f[Frontend]
+    b[Backend]
+    w[Web component]
+    u --> g
+    g --> f
+    g --> b
+    g --> w
+```
+
+### API gateway
+
+The API gateway is a ready-to-use component and the only exposed interface for accessing the application.
+It manages all requests and routes them to the respective development components like frontend and backend.
+Besides that, it also handles cross-cutting concepts like authentication using a SSO.
+
+See [API-Gateway](./gateway.md) for further information.
+
+### Frontend
+
+The frontend provides the application UI and is developed with Vue.js. It calls the backend (via the API gateway) for reading and modifying data.
+It's developed separate for each application and therefore a default template is provided.
+
+The template is described [here](https://refarch-templates.oss.muenchen.de/frontend).
+
+### Backend
+
+The backend provides a REST-API for reading and modifying application data, handles business logic and access to databases.
+Like the frontend the backend is also provided as a template.
+
+The template is described [here](https://refarch-templates.oss.muenchen.de/backend).
+
+### Web component
+
+The web components template enables development of modular frontend components which can be integrated into other applications.
+This concept is also known as micro frontends. By default, most applications won't require this template.
+
+The template is described [here](https://refarch-templates.oss.muenchen.de/webcomponent).
+
+## Enterprise Application integration (EAI)
+
+Beside the development of web applications, the RefArch also provides a template for enterprise application integration (EAI). 
+This enables integration between existing applications. By default, most applications won't require this template.
+
+The template is described [here](https://refarch-templates.oss.muenchen.de/eai).