# Concepts

> The words Quasar uses, and what they mean.

Source: https://quasar.achaverot.fr/docs/concepts/

Quasar has a small vocabulary. These are the words the rest of the documentation uses.

## Application

Anything Quasar runs for you: one container, or several. Every application has a name, a subdomain, an environment, storage, logs, a deployment history, and a page of its own in the dashboard.

There are three ways to create one — from an image, from a Git repository, or from a compose file — but whatever the mode, the result is an application, with the same controls.

See [deploying an application](/applications/deploying/).

## Stack

An application made of several containers, described by a `docker-compose.yml`: an app with its database and its cache, for example.

Quasar routes the domain to **one** service of the stack, and adapts the file to run behind Traefik. The others keep working on the internal network.

See [compose stacks](/applications/compose/).

## Raw application

An application that doesn't speak HTTP: a game server, a database. Traefik only routes HTTP, so these publish their own port and are reached at the **server's address and that port**, not at a subdomain.

## Catalogue entry

A ready-made description of a service: which image or compose file to run, on which port, with which environment. Picking one fills in the new-application form; you still review it before creating anything.

Quasar ships about 60 entries, and you can [add your own](/catalogue/custom/).

An entry is **data**: it says what to deploy, and nothing more.

## Station

A catalogue entry **plus a control panel**: tabs, tables, forms and buttons written for that service in particular, backed by a script.

The application it deploys is an ordinary application. The station adds a tab at the top of its page, and removing the station leaves the application running.

A station is a **program**, so it declares what it is allowed to reach on your server, and you accept that list before installing it.

See [what a station is](/stations/overview/).

| | Catalogue entry | Station |
| --- | --- | --- |
| Says what to deploy | yes | yes |
| Adds a page of controls | no | yes |
| Contains code | no | yes, a script |
| Asks for permissions | no | yes, accepted at install |

## The pieces on the server

| Piece | Role |
| --- | --- |
| **Dashboard** | The Quasar binary: the web interface, deployments, monitoring, backups. |
| **Traefik** | Routes each domain to its application, and gets the certificates. |
| **Socket proxy** | Limits what the dashboard can ask Docker to do. |

Everything lives in `/opt/quasar`. See [files on the server](/reference/server-layout/).