Thea,
Sure here's the "nutshell" version.
We'll license you the software to use for one site, wherever you want to host it. You are responsible for the installing and configuration of the site. We'll provide guidance, instructions, support billed on a per incident basis.
For example:
1) You may choose the DIY option, and host the site on a third party server and install it yourself.
2) You may host with a third party but pay us to install it for you.
3) You may host with us, install yourself ... or pay us to install.
With the DIY version every step is optional - you can pay for just what you need.