That's the new URL for planning media buys on the Google Display Network.
If you are an Adsense publisher, that is where your visitors might come from, and where they will find your competitors.
If you understand what planner/buyers can look for then you have a better chance of serving it up to them.
This is a "plan" for the old faithful "dog training" sector in the US.
You can plan : Audience
And within those you can choose :
Region (Can be country, state, zip, DMA)
Language (Large number of choice)
Age (Age bands)
TLD's (Choose only .com's .edu's etc.)
Formats (Text, display, video)
Display options (3rd party ad serving)
Display sizes (All sizes)
Above or below the fold (aka visibility)
Browser Class (WAP, Tablet, Desktop)
Are you ready?