The scaffold generator did quote a lot for you.
Generated a Post migration - The migration is what creates database tables and columns. Look for the new posts migration in app/db/migrations. If you wish to add any more database columns related to a post, add them to this migration.
Generated a Post model - The Post model is where you should add any validations to data. You can find the model generated by the scaffold generator at app/models/post.rb.
Generated a Post controller - The Post controller contains all actions to view, edit and create new blog posts. You can find it at app/controllers/posts_controller.rb.
Generated views for the Post controller - These can be found in app/views/posts.