docs: add workload configuration guide

docs/guides/workload-configuration.md

@@ -0,0 +1,36 @@
+# Workload Configuration
+
+One of the core purposes of Threeport is to manage the delivery of application
+dependencies:
+
+* Infrastructure: The compute, network and storage resources needed to run your
+  application and its dependencies.  For example, on AWS these include EC2
+  instances, VPCs and EBS volumes.
+* Runtime: The software the provides the environment for your software to run
+  in.  For example, we treat Kubernetes as a runtime environment and manage it
+  to support your applications.
+* Workload Dependencies: The software that runs on the infrastructure and
+  runtimes to support your workloads.
+  * Support Services: Those services installed on the runtime next to your
+    workloads that provide important services.  For example, we use
+    [cert-manager](https://cert-manager.io/) to provision and manage TLS assets
+    for your workload.  Cert-manager runs in the runtime where your workloads
+    reside.
+  * Managed Services: Those services managed by a 3rd party that your
+    workloads rely on.  If you use AWS Relational Database Service to run a
+    database for your workload, this falls into this category.
+  * Workloads: In a distributed or microservices architecture, you may develop
+    many different services that, collectively, serve your end users.  As such,
+    you can define other workloads as dependencies so they be managed
+    holistically.
+
+### Note
+
+The terms "application" and "workload" are often used somewhat interchangeably.
+We use the term "workload" to refer to a single piece of software that can be
+deployed independently.  In contrast, an "application" refers to all the
+workloads that constitute the software that serves the end user.  This is most
+applicable with distributed systems where multiple workloads constitute a
+distributed application.  But even most "monolithic" applications have a
+distinct database workload that runs separately from the core service.
+