docs: tweaks

README.md

@@ -1,6 +1,6 @@
 <div align="center">
-  <img src="https://github.com/microlinkhq/cdn/raw/master/dist/logo/banner.png#gh-light-mode-only" alt="microlink logo">
-  <img src="https://github.com/microlinkhq/cdn/raw/master/dist/logo/banner-dark.png#gh-dark-mode-only" alt="microlink logo">
+  <img src="https://github.com/microlinkhq/openkey/raw/master/design/banner.jpg#gh-light-mode-only" alt="microlink logo">
+  <img src="https://github.com/microlinkhq/openkey/raw/master/design/banner.jpg#gh-dark-mode-only" alt="microlink logo">
   <br>
   <br>
 </div>
@@ -11,6 +11,19 @@
 
 > an AWS Gateway replacement for usage plans and keys for your HTTP API endpoint
 
+## Concepts
+
+<div align="center">
+  <img src="https://github.com/microlinkhq/openkey/raw/master/design/concepts.jpg#gh-light-mode-only" alt="microlink logo">
+  <img src="https://github.com/microlinkhq/openkey/raw/master/design/concepts.jpg#gh-dark-mode-only" alt="microlink logo">
+</div>
+
+**openkey** orbits around three concepts:
+
+- **Plans**: Represents the quota, rate limit, and throttle information specified as a plan.
+- **Keys**: Represents the credentials used during the authentication step and which plan is associated.
+- **Usage**: Keep track of how much plan is available and consumed with the associated key.
+
 ## FAQ
 
 ### Why?