In digital imaging terms, ‘artifacts’ are usually those little noisy clusters of pixels most noticeable in images (most JPGs, for example) along higher contrast edges. It’s an artifact of the compression process. Much more noticeable when you zoom in
Also, images that have been cropped or processed either in camera or out, to enhance detail or reveal detail in shadows or highlights, or contain large, subtle gradations, are also very prone to producing artifacting. Virtually all video frame captures will also include artifacts.
There are also many physical artifacts caused by lighting, reflections, lenses and even camera sensors.
Learning to control, avoid, and correct (when possible) artifacting is a definite skill to develop for photographers, even though the cameras are smarter than ever.
I suspect that the most common and frustrating type of artifacting for IDers is too few pixels, or too blurry or too noisy, or too low contrast details.
Pixel quantity and noise levels usually have some dependence on each other in most cases. Notice that I’m avoiding the term ‘resolution’ here as it’s a source of a lot of the confusion (and always has been!).
I would be willing to put together some basic guide (tip sheet with examples, perhaps) for iNat to help beginners learn how to deal better with this stuff.
If you’re an IDer and have some examples of both good and bad submissions on this topic, I would appreciate hearing from you.