docs: move docs branch sections from readme to contrib guide

docs/CONTRIBUTING.md

@@ -228,6 +228,37 @@ Add "WIP" (Work in Progress) or "Draft" to the title if the PR is not yet ready
    ```console
    git branch -d <branch-name>
    ```
+
+## Choosing the correct branch when contributing
+
+New writing goes to the `main` branch and can be viewed on the Releases -> development dropdown menu.
+We have staging and production levels for our documentation which are as follows:
+
+1. Development documentation aka staging (build of `main` branch) - [link](https://main.lifecycle.keptn.sh)
+2. Official documentation aka production (build of `page` branch) - [link](https://lifecycle.keptn.sh)
+
+Let's take a look what happens when your changes are merged in `main` and `page` branch respectively.
+
+### Development documentation (Staging)
+
+This page reflects the current development status of the documentation.
+It will be built regularly and can be easily accessed.
+
+- build: on each push to `main` with documentation changes
+- build-environment: main
+- config folder: [main](./config/staging/)
+
+It should allow bleeding-edge users and contributors to see the current state and help with debugging etc.
+
+### Official documentation (Production)
+
+This documentation set contains all released versions of KLT and is stored in an orphaned branch called `page`.
+
+- build: on each push to `page` with documentation changes
+- build-environment: production
+- config folder: [production](./config/production/)
+
+A new version is generated when we push the `main` branch to production - hence old `page` branch will be copied over a “version” folder and it doesn't overwrite changes that were only pushed to `page`.
 
 ### Developer Certification of Origin (DCO)