What does the at sign mean when listing files with ls?

Question

When copying files with cp command on Mac OSX Mavericks and then looking at them ls command I sometimes see an @ sign in the listing.

What does it mean please?

For example:

# cp -v ~/Desktop/ios-newbie/oauthGoogle/oauthGoogle/Google.* .
/Users/admin/Desktop/ios-newbie/oauthGoogle/oauthGoogle/Google.h -> ./Google.h
/Users/admin/Desktop/ios-newbie/oauthGoogle/oauthGoogle/Google.m -> ./Google.m

# ls -al
total 88
drwxr-xr-x  12 admin  staff   408 Jan 27 10:18 .
drwxr-xr-x  18 admin  staff   612 Jan 27 10:17 ..
-rw-r--r--   1 admin  staff   114 Jan 27 10:17 Facebook.h
-rw-r--r--   1 admin  staff  2815 Jan 27 10:17 Facebook.m
-rw-r--r--@  1 admin  staff   112 Jan 27 10:18 Google.h
-rw-r--r--   1 admin  staff  3554 Jan 27 10:18 Google.m
-rw-r--r--   1 admin  staff   112 Jan 27 10:18 Mailru.h
-rw-r--r--   1 admin  staff  3364 Jan 27 10:18 Mailru.m

Here the screenshot of the same example: