What does a + mean at the end of the permissions from ls -l?

What is the plus sign at the end of the permissions telling me?

ls -l
total 4
drwxrwxrwx+ 2 benson avahi-autoipd 4096 Jan 27 17:37 docs

Here's the context:

cat /etc/issue
\CentOS release 5.3 (Final)
Kernel \r on an \m