This was previously discussed on the thread on the USGS announcement [1], but this NYT article has more information and pictures.
As for impact, this discovery (if confirmed!) isn't all that earthshattering from the perspective of a layperson. It just pushes back the existence of already well-established pre-Clovis cultures several thousand years.
What makes it potentially exciting to archeologists is that these dates present some potential issues with the coastal migration hypothesis, the current "dominant" understanding because current paleoclimate models indicate that things prior to 18kya were too icy for short range coast hopping to work. Either those models are wrong in some way or we've been looking for evidence in the wrong ways. There may also be some knock on effects for a few other things, but it'll all get worked out over the next few years.
[1] https://news.ycombinator.com/item?id=28642050
