How to change vertices on a circle? Just a quick little question, in this video

https://www.youtube.com/watch?v=CVPcT0dJmoY

At around 41:20 he someone makes it so he can edit the vertices on the circle, but he never says what button he hits to do it, and I've been googling and I can't find it.
He's in edit mode, try pressing the Tab button to enter it.

By the way, I'd absolutely recommend you checking out this tutorial, especially the first 2-3 lessons. It goes in detail about Blender UI and all its menus and submenus.