Lol! Several come to mind!
It's an old term I use to describe something that is on or hot for example the burner on your stove is hot when it is on and cold when off.
In the past one couldn't make a disk image while windows is hot
due to locked files being used by windows at the time.
Hence most aftermarket imaging software come on a bootable disk which puts you in a DOS like environment to perform disk imaging among other things. Although newer versions do have a GUI to use like True image for example. With windows not running there's no locked files to contend with.
I imagine that windows 7 has a work around this now but still windows is running from what I've seen on YouTube videos of windows 7 imaging.
With the aftermarket imaging software you have the ability to omit certain files or folders from the image if you want like the pagefile.sys for example.
Granted I don't know enough about windows 7 imaging to appreciate its use as I've been on windows vista until a few months ago.
I am behind the times, a day late and a dollar short. Playing catch up now.