The Significance of Pentecost

There is a oracular and an oral aspect to what's going on at Pentecost. They're not bearing the message of a king or a figure that who is now dead, but actually a living king who reigns and rules and who will come again. It changes everything. So speak more about that, especially as we turn into chapter two. There's kind of a big event that happens in chapter two. How do you describe that? What's the significance of Pentecost?