Basically, Ukraine pulled off a bunch of troops and reserves from the already collapsing front in Donbas, and made an incursion into Kursk. I imagine they are starting to panic because Russia is now visibly on offensive, meanwhile world attention is shifting to West Asia. So, this stunt was likely intended to put them back in the spotlight, and to try and paint a picture that Ukraine still has offensive capacity. Looks like they allocated something like 12k troops to it, and the nuclear power plant in the region might've been the target. However, predictably they didn't get far, and at this point it looks like Russia has the initiative.
I think this was a disastrous miscalculation on Ukraine's part. They were already in a weak position where they couldn't hold the front, and the troops and machinery they allocated to this, would've been much better used to support their collapsing positions. Instead, they threw them into the open where it's much easier for Russian army to engage them. Wasting manpower at this scale when you're already on a back foot is not a smart move. Once Russians push them out of Kursk, it's almost certain that they will proceed to open another front in Sumy region. This is something that Ukraine can ill afford.
All that said, the most dramatic developments are happening around Pokrovsk where it looks like Russia will be able to make it all the way to Dnepr. Once that happens, Ukrainian army will be split in two limiting the ability to support and reinforce where needed. At that point we'll likely start seeing general collapse of the AFU.
So, we're likely seeing history on repeat here where the battle of Kursk will once again prove to be decisive.