Now that you have created your first Rails App and started looking inside the application directory we know some of you hunger for the details of all the folders and files generated. So here is a quick rundown of what in each directory. Take your time and explore away.
app is where you'll put the majority of your application code. You'll be spending alot of time in here. Rails is very opinionated software so it place a lot of emphasis on keeping code organized, so the app directory has a number of sub-directories:
assets contains sub-directories where you'll store your application's images, JavaScript files, and stylesheets (CSS)
channels is where you put Ruby classes designed to handle real-time features using Action Cable
controllers is where you will organize your Controller code (i.e. the C in mvC)
helpers is where Ruby modules that define utility methods for views are kept
jobs is where Ruby classes for running background jobs are kept
mailers is where you put Ruby classes for generating and sending emails
models is where you will organize your Model code (i.e. the M in Mvc)
views is where you will organize your View code (i.e. the V in mVc)
bin contains rails script files and binaries. You will not be messing around this folder.
config is where you go to tweak the configuration settings of your application. Rails sets 'sensible defaults' for your app, so you wont initially need to edit anything in here. But later on you will use this directory to fine tune your app. Some of the more important files in here include,
database.yml configures the database used by each environment
environments is a directory that contains 3 files that define specific settings for each environment: development, test, and production
initializers is a directory where you put Ruby code that needs to be run when the application starts
routes.rb maps incoming requests (URLs) to application code
db contains everything related to the database, including migration files and in the case of using the default SQLite3 database the database file itself.
lib is where you put any reusable "library" code that's not a model, view, or controller. An important subdirectory is,
tasks is where you put any custom Rake tasks for your application. Each file has a .rake extension
log is where Rails automatically creates log files. These files keep an audit log of what happened when your app ran. Each environment gets its own log file
public is the document "root" directory of the app. It contains static files that are served directly by the web server. For example the notorious Not found error page (404.html) lives here and gets served when a page can't be found.
test is where you put test files if you use the default test library. This is not used by RSpec
tmp is where Rails stores any temporary files needed by the app. You wont need to go into this directory
vendor is more of a legacy directory where third party code used to live. Now a days we use gems instead
Gemfile - this file contains a list of third-party dependencies (Ruby gems) that your application needs