docs: restructure sections and add networking information

docs/.pages

@@ -1,5 +1,5 @@
 arrange:
   - index.md
-  - commands.md
-  - defaults.md
-  - faq.md
+  - usage
+  - internals
+  - faq

docs/faq/.pages

@@ -0,0 +1,3 @@
+title: FAQ
+arrange:
+  - faq.md

docs/internals/.pages

@@ -0,0 +1,4 @@
+title: Internals
+arrange:
+  - defaults.md
+  - networking.md

docs/internals/networking.md

@@ -0,0 +1,28 @@
+# Networking
+
+- Related issues:
+    - [rancher/k3d #220](https://github.com/rancher/k3d/issues/220)
+
+## Introduction
+
+By default, k3d creates a new (docker) network for every new cluster.
+Using the `--network STRING` flag upon creation to connect to an existing network.
+Existing networks won't be managed by k3d together with the cluster lifecycle.
+
+## Connecting to docker "internal"/pre-defined networks
+
+### `host` network
+
+When using the `--network` flag to connect to the host network (i.e. `k3d create cluster --network host`),
+you won't be able to create more than **one master node**.
+An edge case would be one master node (with agent disabled) and one worker node.
+
+### `bridge` network
+
+By default, every network that k3d creates is working in `bridge` mode.
+But when you try to use `--network bridge` to connect to docker's internal `bridge` network, you may
+run into issues with grabbing certificates from the API-Server. Single-Node clusters should work though.
+
+### `none` "network"
+
+Well.. this doesn't really make sense for k3d anyway ¯\_(ツ)_/¯

docs/usage/.pages

@@ -0,0 +1,4 @@
+title: Usage
+arrange:
+  - commands.md
+  - guides

docs/usage/guides/.pages

@@ -1,4 +1,4 @@
-title: Examples
+title: Guides
 arrange:
   - exposing_services.md
   - registries.md