docs: update README

Add more detail about what rhc does, its history and some non-goals.

Signed-off-by: Link Dupont <link@sub-pop.net>

README.md

@@ -1,2 +1,34 @@
-rhc is a client that registers a system with RHSM and activates the Red Hat yggd
-MQTT client.
+`rhc` is a simple, one-step front-end client for Red Hat connected services. It
+is built to be an alternative client to `subscription-manager`,
+`insights-client`, and any other client utility that enables connecting a system
+to Red Hat services.
+
+It currently performs 3 steps when it connects a system:
+
+1. Registers the system with Red Hat Subscription Management. If the system is
+   already registered, this step is a noop and it moves to the next step.
+2. Registers the system with Red Hat Insights. If the system is already
+   registered, this step is a noop and it moves to the next step.
+3. Activate the `rhcd` daemon.
+
+Likewise, when rhc is disconnecting a system, it performs the steps in
+descending order.
+
+1. Deactivates the `rhcd` daemon.
+2. Unregisters the system from Red Hat Insights.
+3. Unregisters the system from Red Hat Subscription Management.
+
+`rhc` (the front-end client) is not the same thing as
+[`yggdrasil`](https://github.com/RedHatInsights/yggdrasil). `rhc` began
+as a program within the `yggdrasil` project, but has since been forked out.
+`rhc` still has a soft dependency on `yggdrasil`; `yggdrasil` provides `rhcd`
+(or `yggd`), the daemon that `rhc` activates as the last step in its connection
+process.
+
+## Non-goals
+
+* `rhc` will never be a 100% compatible drop-in replacement for
+  `subscription-manager`, `insights-client`, or any other Red Hat connected
+  services command-line utility.
+* Complexity; `rhc` is deliberately designed to be simple, and as "hands-off" as
+  possible.