Add explanation of the app

Author: StephanSchmidt

README.md

@@ -14,6 +14,26 @@ capabilities.
 - Install Go https://go.dev/doc/install
 - Run `make` to run the application
 
+## Application
 
+The application is a todo list application.
 
+The application is a Go application with a simple REST API and a simple
+frontend in JavaScript. 
+
+The frontend is in the `internal/js` folder and is a simple single page
+application that allows you to add todos to the todo list. The JavaScript
+application is delivered with a Golang embedded filesystem.
+
+The frontend uses [Alpine.js](https://alpinejs.dev/) as the JavaScript framework.
+
+The Go backend is in the `internal/todo` folder and contains the following:
+
+- `db`: The database models and the database access functions. 
+- `usecase`: The use cases of the application.
+- `web`: The HTTP handlers of the application.
+
+The database is SQLite with [GORM](https://gorm.io/) as the database access library.
+
+The *_module.go files are the entry points for each module.