Updating README to explain how things work

README.md

@@ -16,7 +16,15 @@ insertCassette(cassette);
 
 ## Creating a recording
 
-* in a QUnit test click on the "Record API Queries checkbox
+* in a QUnit test click on the "Record API Queries" checkbox (typically you should do it on the global test route)
 * when the tests are finished a file will automatically be downloaded
 * replace the current cassette.js in tests/helpers with the new cassette.js
 
+
+## How it works
+
+* When record is set to true, every ajax response is monitored and saved to an array.
+* Within one recording session responses are cached, so you will only hit the same endpoint once.
+* At the end of the session a "cassette" is saved in the format that Sinon Fake server expects.
+* If record is not true, Sinon Fake server is pre-loaded with your already recorded cassette.
+* If something has not been recorded, it will be downloaded at the end of a test run. The new cassette can be manually merged.