What's the 'Start' button in Win 8.1?

I'm getting confused about the new start button that was supposedly to come with the Win 8.1 update. I cant' find anything different from Win 8. Is the start button the icon found in the lower left corner of the screen?...or on my computer keyboard?...it looks like a window. I was expecting that I would get a dropdown start menu with Win 8.1 like I get with Win 7 when I click on that button. I would really like to have the Win 7 dropdown start menu when I click on that button in 8.1.
Thanks.