Difference between resource and resources in rails routing?

In essence, routing resources is when resources gives action abilities to a controller.

http://guides.rubyonrails.org/routing.html#specifying-a-controller-to-use

If a pluralized resources is used as a way to handle generic requests on any item, then a singular resource is a way to work on the current item at hand.

So in other words, if I have a collection of Apples, to retrieve a specific apple, I'd have to tell the router "Apples" what apple to retrieve by sending the ID of the apple. If I already have one Apple, then an ID is not needed.

Notice the differences between the two by looking at what actions (or routes) they have:

• resources: Index, new, create, show, edit, update, destroy
• resource: new, create, show, edit, update, destroy

In your example:

1. The controller "geocoder" is a singular resource that you can use to edit, create, update, etc.
2. The controller "posts", is a plural resource that will handle incoming generic posts that you can index, edit, create.. etc

Singular Resources:

Sometimes, you have a resource that clients always look up without referencing an ID. For example, you would like /profile to always show the profile of the currently logged in user.

Or, Normally your currently logged-In user belongs to a single organization, so to goto his/her organization profile page there can be two routes

#1
/organizations/:id

#2
/organization #simply

Here, the later implementation makes more sense; isnot it? you get the organization object from association

# in organizations#show
@organization = current_user.organization

To define such singular resource you use resource method: Example

# in routes.rb
resource :organization

creates six different routes in your application, all mapping to the Organizations controller:

whereas, you define plural resources using resources method

resources :organizations