What is the deal with the plus (+) sign in Google search?

I just don’t see the point. For those who don’t know what I’m talking about, if your search term is more than one word, it adds a plus between each word. Why is this? Did they do that to bring new ways to manipulate search? Is it just something obvious that I’m missing? Is there any way I can disable this feature? I know it’s not important in the big scheme of things, but it’s an annoying addition IMO.

And while we’re on the subject, what’s the deal with the tabs being on the left column now?