When using CRUD and MVC something important to note is the difference to the new/edit action versus the create/update action.
The difference is that a new and edit action simply renders a form. The create and update action handles the action of editing the database. The create action inserts data into the database and the update action will update the database.
Simple concept, but as I practice creating routes in rails I realized how important knowing these concepts are when building an MVC/CRUD application.