diff --git a/avr/README b/avr/README
index b9f1983..57ae96f 100644
--- a/avr/README
+++ b/avr/README
@@ -16,6 +16,12 @@ With full AqHome network stack (including address assignment protocol):
 - <300 bytes SDRAM (including network buffers)
 
 
+A full system consists of these elements:
+- device main app (main device code provided by the user providing full control to the developer)
+- modules (basically drivers implementing support for hardware devices like sensors or displays)
+- apps (internal apps combining and extending functionality of driver modules)
+
+
 The following system routine types are defined:
 
 Function   I  Description                                    I required I add to file