docs: merge core_concepts.md and core-concepts.md

docs/core-concepts/core-concepts.md

@@ -1,21 +1,50 @@
-# Tool, State, and Resource
+# Core Concepts Overview
+
+Let's assume you're familiar with core Git, Docker, Kubernetes, Continuous Integratoin, Continuous Delivery, and GitOps concepts. 
+These are the core concepts of DevStream.
+
+## The Architecture of DevStream
+
+The architecture image below shows how DevStream works in general:
+![](./images/architecture-overview.png)
+
+## Workflow
+
+![config state resource workflow](../images/config_state_resource.png)
+
+## Config, Tool, State and Resource
 
 The architecture documentation explains how in general DevStream works. If you haven't read it yet, make sure you do that before continuing with this document.
 
-## 1 Tool
+### 1. Config
+
+DevStream defines your DevOps toolchain in config files.
+
+The major part of the config file is definition of your DevOps _Tools_.
+
+Each _Tool_ has its name, instanceID (unique identifier), and options for that tool.
+
+Each _Tool_ can also have its dependencies, and can refer to other tool's output as values of its own options.
+
+### 2. Tool
+
+//TODO(daniel-hutao): @IronCore Please help to update the descriptions below.
 
 - One of the major part of the _Config_ is a list of tools, defined in [here](https://github.com/devstream-io/devstream/blob/main/internal/pkg/configloader/config.go#L23).
-- Each _Tool_ has its Name, Plugin, and Options, as defined [here](https://github.com/devstream-io/devstream/blob/main/internal/pkg/configloader/config.go#L40).
+- Each _Tool_ has its Name, InstanceID, and Options, as defined [here](https://github.com/devstream-io/devstream/blob/main/internal/pkg/configloader/config.go#L40).
 - Each _Tool_ can have its dependencies, which are specified by the `dependsOn` keyword.
 
-The dependency `dependsOn` is an array of strings, with each element being a dependency. Each dependency is named in the format of "NAME.PLUGIN". See [here](https://github.com/devstream-io/devstream/blob/main/examples/tools-quickstart.yaml#L12) for example.
+The dependency `dependsOn` is an array of strings, with each element being a dependency. Each dependency is named in the format of "TOOL_NAME.INSTANCE_ID". 
+See [here](https://github.com/devstream-io/devstream/blob/main/examples/quickstart.yaml#L22) for example.
+
+### 3. State
 
-## 2 State
+The _State_ records the current status of your DevOps toolchain. It contains the configuration of each tool, and the current status.
 
 - The _State_ is actually a map of states, as defined [here](https://github.com/devstream-io/devstream/blob/main/internal/pkg/statemanager/state.go#L24).
 - Each state in the map is a struct containing Name, Plugin, Options, and Resource, as defined [here](https://github.com/devstream-io/devstream/blob/main/internal/pkg/statemanager/state.go#L16).
 
-## 3 Resource
+### 4. Resource
 
 - We call what the plugin created a _Resource_, and the `Read()` interface of that plugin returns a description of that resource, which is in turn stored as part of the state.
 

mkdocs.yml

@@ -79,7 +79,6 @@ plugins:
 nav:
   - Overview: 'https://docs.devstream.io'
   - 'understanding_the_basics*.md'
-  - 'core_concepts*.md'
   - 'quickstart*.md'
   - DTM Commands Explained in Depth:
     - commands/autocomplete*.md