Challenge 1: Tour the Generated App — Solution

app/       — Holds your application's actual code: controllers (request
             handling), models (Active Record classes mapped to database
             tables), views (ERB templates rendered as HTML), and assets
             (CSS/JS/images) — the M, V, and C of MVC, plus supporting code.

config/    — Application-wide configuration, most importantly routes.rb
             (which URLs map to which controller actions) and
             database.yml (database connection settings per environment:
             development, test, production).

db/        — Everything related to the database schema itself: the
             migrate/ folder holds individual migration files (each one a
             small, ordered change to the schema), and schema.rb is the
             current, combined snapshot of what the database looks like
             after all migrations have run.

Gemfile    — Declares the project's gem dependencies (Ruby Course 2,
             Chapter 7) — Rails itself is listed here as a dependency,
             along with the database driver, and any other gems the
             project needs.

=begin
Notes:
- Every one of these four things already exists immediately after
  rails new finishes, with no manual setup required — this is the
  starting point for the "convention over configuration" theme running
  through the rest of the course.
- Compare this to Express, where none of this structure is generated for
  you; express1-8 covered manually designing and creating an equivalent
  src/ layout from scratch.
=end