Ping generally means how well your connection responds back and forth with the server. In his example, it takes an average of 55ms (55 thousandths of a second) to respond. So those who would have 300ping would need to take .3 seconds to respond to the server. While you think "feh, that's not that bad", well take that, and apply it to every condition that the server checks for before uploading the page. It gets to be a hassle when you have a slow connection speed.
And I stopped looking for threads after page 12 (!) of this forum, but these were some examples of threads on the subject... wonder why they all got locked?