What is the ALEPreviewWindow file?

[xmready]

When using :ALEDetaila file is created in my working directory named ALEPreviewWindow. I appears to be empty and I can't seem to find any documentation on this file. I would like to know:

1. What does it do?
2. Why does it persist after closing vim?
3. How can I set a different directory for it to be saved in, as opposed to my working dir?