Let me do my best to try to answer your question/s, Bill.
The goal, hopefully, is to create or find an image which is 'wider' than a 'normal' field-of-view, or FOV. Where I, and many photographers, get into trouble, is trying to define 'normal'. But, traditionally (and these definitions date back to the analog days when many photographers were shooting film on 35mm cameras) a 'normal' FOV would have been usually somewhere between 50mm and 55mm. 40mm is on the wider side of normal but is still considered by many to be within the realm of 'normal'. Another way to think of it is that normal lenses roughly match the dimensions and perspective of what the human eye normal sees or perceives.
But of course if you think about this for all of 10 seconds, it falls apart - since our human binocular vision encompasses a field of view much wider than that of a traditional 50mm lens. However the definition holds up when you start thinking about what wide angles - or at least wider angles - do. Not only do they show a wider field of view but often (though not always) they either partially or greatly distort the image.
Then of course there is a whole school of photographers, including Henri Cartier-Bresson, for whom the slightly wider FOV of a traditional 35mm lens, comes closer to a 'normal' view of the world. So where does one draw the dividing line?
For the purposes of this Challenge, I hope all entries will be made with lenses wider than the traditional normal FOV's - which basically means anything w-i-d-e-r than the so-called normal focal lengths (40-55mm). So if you were shooting with micro 4/3 gear, which has a built-in 'crop factor' of 2x - then any mu43 lens or focal length WIDER than 20mm would qualify as a 'wide angle'. When one applies the crop factor of 2x to the popular Panasonic 20mm pancake lens, you get an FOV equivalent to 40mm - which still falls within my admittedly subjective category of being a 'normal' lens. But if you used either a 17mm lens or a 14mm one - you'd have the equivalent of a 35mm lens or a 28mm lens - both of which definitely qualify as 'WIDE'.
Furthermore, wide-angles traditionally do or accomplish things that 'normal' lenses can't or don't. A wide angle should - or at least can - allow more visible space to be included in the frame. There are also tricks and effects of perspective associated w/wider angles. Usually objects closer to us or the camera lens should or may appear larger vs. those farther away which, though they may actually be the same size as the foreground objects, will appear much smaller in a wide angle shot (than they will when seen via a 'normal' lens).
Then there are technical/millimeter theories. In traditional 35mm analog film, the diagonal measurement of the negative I think is 43.3mm. Once the focal length of the lens gets shorter than this, it (supposedly) gets classified as a wide angle. 35mm, 28mm and 24mm focal lengths used to be more commonly used wide-angles; then there are the ultra-wide-angle focal lengths of 20mm or 21mm, 17mm or 18mm, or the extreme 14mm.
Whew. A person could get seriously deranged thinking too much about this. My hope is that in this Challenge, we can be creatively subjective - and find ways to use, show or create a 'wide' view of something which is wider than a more normal perspective. I know for example that I've used some of my wide angle lenses to take extreme close-up or macro photographs which, when you look at them, don't convey a feeling of 'wide' or of 'wideness' at all. So it's not just the lens or focal length; there should be a degree of creative freedom to interpret this Challenge in a way that makes sense to each of us. If one happens to be the kind of photographer who normally shoots tightly cropped portraits with moderate telephoto 'portrait' lenses, that person's wide or wider angle might be closer to another photographer's normal FOV. But in general, I would hope that most entries would make use of one of the traditional 'wider' focal lengths.
Thanks again for the question, Bill. Not an easy one to answer as, obviously, there are multiple correct or differing interpretations. But I hope this helps a little.
Miguel