[getting started] specify which kind of temporary files are stored in the /tmp folder

guides/source/getting_started.textile

@@ -138,7 +138,7 @@ application. Most of the work in this tutorial will happen in the +app/+ folder,
 |README.rdoc|This is a brief instruction manual for your application. You should edit this file to tell others what your application does, how to set it up, and so on.|
 |script/|Contains the rails script that starts your app and can contain other scripts you use to deploy or run your application.|
 |test/|Unit tests, fixtures, and other test apparatus. These are covered in "Testing Rails Applications":testing.html|
-|tmp/|Temporary files|
+|tmp/|Temporary files (like cache, pid and session files)|
 |vendor/|A place for all third-party code. In a typical Rails application, this includes Ruby Gems and the Rails source code (if you optionally install it into your project).|
 
 h3. Hello, Rails!