title: Ruby on Rails Callback, what is difference between :before_save and :before_create?
body: <p>Could you explain in detail what the <code>:before_save</code> and <code>:before_create</code> Ruby on Rails callbacks are, and what they have to do with Rails validations? Does validation occur after <code>:before_save</code> or <code>:before_create</code>? </p>