doc: describe how we expect the system to be deployed

Add some more information around how we expect the system to be deployed
using the deployment guide.

docs/deploy-guide/index.md

@@ -6,10 +6,55 @@ focus is on deploying bare metal in data centers with functional DCIM and IPAM.
 
 ## About the Guide
 
-This guide is not meant to be a definitive guide to [GitOps][gitops] and
-how it can be used with UnderStack or even a best practices example
-but instead focused on an example _development_ oriented installation.
+While the deployment of UnderStack leans heavily into [GitOps][gitops],
+it is not meant to be a definitive guide to [GitOps][gitops]. It is also
+not the only way GitOps can be used with UnderStack but instead focuses on
+one example deployment installation.
 It will make a few assumptions and some opinionated choices that may
-not align with a production best practices installation.
+not align with a production best practices installation. Improvements are
+always welcome.
+
+## System Division
+
+A fully deployed UnderStack is divided into 3 distinct parts or environments
+that are referred to in the documentation as:
+
+- Management
+- Global
+- Region(s)
+
+```mermaid
+flowchart TD
+
+  A[Management] --> B[Global];
+  B[Global] --> C[Region A];
+  B[Global] --> D[Region B...];
+  B[Global] --> E[Region N];
+```
+
+A fully functioning system only needs one Management environment, one Global
+environment and one or more Regions. In this configuration the Management
+environment is responsible for utilizing the [GitOps][gitops] tool to deploy
+the expected state to all other environments. The Global environment is
+responsible for hosting any services that are expected to exist only once
+for a whole system deployment such as the DCIM/IPAM tool. While the Region
+environments will run the tools and services that need to live close to the
+actual hardware.
+
+In fact one Management environment can control multiple systems if you have
+a staging environment and a production environment for example.
+
+```mermaid
+flowchart TD
+
+  A[Management] --> |staging| B[Global];
+  B[Global] --> C[Region A];
+  B[Global] --> D[Region B...];
+  B[Global] --> E[Region N];
+  A[Management] --> |prod| F[Global];
+  F[Global] --> G[Region A];
+  F[Global] --> H[Region B...];
+  F[Global] --> I[Region N];
+```
 
 [gitops]: <https://about.gitlab.com/topics/gitops/>