Merge pull request emberjs#836 from emberjs/michaelrkn-patch-1

Further clarify role of adapters

source/models/customizing-adapters.md

@@ -1,19 +1,21 @@
-In Ember Data, the Adapter determines the structure of requests to a
-backend data store, such as the URL format and headers.
-Ember Data's Adapter has some built-in
-assumptions of how a [REST API](https://jsonapi.org/) should look. If
+In Ember Data, the Adapter determines how data is persisted to a
+backend data store, such as the URL format and headers for a REST API.
+(The format of the data itself is determined by the
+[serializer](../customizing-serializers/).)
+Ember Data's default Adapter has some built-in
+assumptions of how a [REST API should look](https://jsonapi.org/). If
 your backend conventions differ from these assumptions Ember Data
 makes it easy to change its functionality by swapping out or extending
 the default Adapter.
 
 Some reasons for customizing an Adapter include using
 `underscores_case` in your urls, using a medium other than REST to
 communicate with your backend API or even using a
-[local backend](https://github.com/rpflorence/ember-localstorage-adapter).
+[local storage backend](https://github.com/locks/ember-localstorage-adapter).
 
 Extending Adapters is a natural process in Ember Data. Ember takes the
 position that you should extend an adapter to add different
-functionality instead of adding a flag. This results in code that is
+functionality. This results in code that is
 more testable, easier to understand and reduces bloat for people who
 may want to subclass your adapter.