This will be the web address of the blog you're adding VideoPress to. It can be your own custom domain or a blog on WordPress.com.
Why do I need a new WordPress.com blog?
When you upload videos (from your self-installed blog), they'll be stored on this new WordPress.com blog. Essentially, this is just a place to store them.
Does VideoPress cost anything?
Yes, it's $59.97 per year which comes with 3GB of storage (You can purchase additional storage if you'd like). There are no additional charges for bandwidth usage or playback.
Blog address: .wordpress.com
Once logged in, you'll re-direct to the checkout where you'll pay for VideoPress.
How does WordPress.com fit in?
When using the VideoPress plugin to upload videos, you'll actually be hosting those videos on WordPress.com.