Gearman is a generic framework to distribute processing jobs to separate processes in the same machine or other machines in a cluster. It allows your application to perform tasks in parallel, balance the processing load, and even invoke code written in other languages. The "Gearman" word is an anagram of "manager". Its purpose is solely to dispatch jobs that need to be executed, but Gearman just by itself does not do anything useful.
In his example he sets up a simple "Hello World" processing queue including the command line to start up the Gearman server and the PHP you'll need to push in a request, grab the status and see the percentage of it that's been completed.