The 720P HD platrorm! What is it for?

MacApp

In the project info under the platform dropdown menu there is there is options for MacBook and 720p H.
What is this 720p HD for?

MacApp

I tried to insert a background image "1280x800" and a message told me that the image is too big and it must be resized.
How it is HD and can't get big images? Can the apps run fullscreen or not?

beefy_clyro

The biggest image you can insert is 1024 x 1024 ... Anything else will be resized down by GS