[ivanbakel]

Deconvolution is any attempt to recover data that has been passed through some known transformation. It can "create new data" because it is effectively mathematically-educated guesswork.

In the case of upscaling an image, deconvolution involves looking for images which, when scaled down, resemble the original image being upscaled. That kind of pre-image approach can be applied to blur as well (if the blur process is deterministic).