Provide an overview of how Promitor works (#1190)

Signed-off-by: Tom Kerkhove <kerkhove.tom@gmail.com>

docs/concepts/how-it-works.md

@@ -0,0 +1,60 @@
+---
+layout: default
+title: How Does Promitor Work?
+---
+
+**Promitor** is an Azure Monitor scraper which makes the metrics available
+to a variety of metric systems such as Atlassian Statuspage, Prometheus and StatsD.
+
+{:refdef: style="text-align: center;"}
+![Promitor](./../media/concepts/high-level.png)
+{: refdef}
+
+## Scraping Azure Monitor metrics
+
+When you want to scrape resources, you can use **Promitor Scraper** which uses a metrics-as-code approach.
+
+By writing a metric declaration, you will define what Azure Monitor metrics to scrape for a set of Azure resources and
+ to what metric sink(s) they should be reported.
+
+Here's an overview of how it works:
+
+{:refdef: style="text-align: center;"}
+![Promitor Scraper without resource discovery](./../media/concepts/how-it-works-without-discovery.png)
+{: refdef}
+
+## Using resource discovery
+
+While Promitor Scraper uses a declarative approach for defining Azure resources to scrape; as of Promitor Scraper 2.0
+ you can integrate with **Promitor Resource Discovery**!
+
+With resource discovery, you can define **resource discovery groups** that represent Azure resources of a given type and
+ optionally define criteria for the resources to comply with.
+
+By doing this, you can **change your metric declaration for Promitor Scraper so that,** instead of using declared resources,
+ **reference a resource discovery group** which be used to determine what Azure resources it should scrape
+ metrics for.
+
+Behind the scenes, Promitor Resource Discovery integrates with **Azure Resource Graph** which will query your Azure landscape
+ to discover the corresponding resources.
+
+Here's an overview of how they work together:
+
+{:refdef: style="text-align: center;"}
+![Promitor Scraper with resource discovery](./../media/concepts/how-it-works-with-discovery.png)
+{: refdef}
+
+## What components do agents provide?
+
+Every Promitor agent provides a REST API which which you can integrate and uses background jobs to acquire the data
+ to reduce latency.
+
+Here's a detailed overview:
+
+{:refdef: style="text-align: center;"}
+![Agent internals](./../media/concepts/agent-internals.png)
+{: refdef}
+
+_(*) Resources are still discovered sychronoursly but this will be implemented in Promitor Resource Discovery v0.2._
+
+[← back](/)

docs/index.md

@@ -6,7 +6,8 @@ title: Promitor - Bringing Azure Monitor metrics where you need them
 [![License](https://img.shields.io/github/license/mashape/apistatus.svg?style=flat-square)](https://github.com/tomkerkhove/promitor/blob/master/LICENSE)
 [![Build Status](https://img.shields.io/azure-devops/build/tomkerkhove/promitor/50/master.svg?label=Scraper%20Agent%20-%20CI&style=flat-square)](https://dev.azure.com/tomkerkhove/Promitor/_build/latest?definitionId=50&branchName=master)
 [![Docker Pulls](https://img.shields.io/docker/pulls/tomkerkhove/promitor-agent-scraper.svg?style=flat-square)](https://hub.docker.com/r/tomkerkhove/promitor-agent-scraper/)
-[![Docker Stars](https://img.shields.io/docker/stars/tomkerkhove/promitor-agent-scraper.svg?style=flat-square)](https://hub.docker.com/r/tomkerkhove/promitor-agent-scraper/)[![Donate](https://img.shields.io/badge/Donate%20via-GitHub-blue.svg?style=flat-square)](https://github.com/users/tomkerkhove/sponsorship)
+[![Docker Stars](https://img.shields.io/docker/stars/tomkerkhove/promitor-agent-scraper.svg?style=flat-square)](https://hub.docker.com/r/tomkerkhove/promitor-agent-scraper/)
+[![Donate](https://img.shields.io/badge/Donate%20via-GitHub-blue.svg?style=flat-square)](https://github.com/users/tomkerkhove/sponsorship)
 
 **Promitor** is an Azure Monitor scraper which makes the metrics available
 for metric systems such as Atlassian Statuspage, Prometheus and StatsD.
@@ -46,6 +47,7 @@ and vote for features!
 
 ## Documentation
 
+- **[How It Works](concepts/how-it-works)**
 - **Metrics**
   - [General Declaration](configuration/v1.x/metrics)
   - [Supported Providers](configuration/v1.x/metrics#supported-azure-services)