Russia has been trying to get this for a few months, estimates show ~30k Russian solider fatalities and over 400 tanks/infantry vehicles.

From what I know it was strategically important to the Donetsk region, which Russia would like to get back under control. It’s also a bragging point for the “election” because it’s the largest advance they’ve had since last May, they pushed a ton of lives through the meat grinder to take it.

source

As to the counteroffensive, there’s a page about it on wikipedia! It wasn’t as successful as they’d hoped, they didn’t even manage to get the minimum goal. They’ve been focusing on taking out the Black Sea fleet, overcoming anti air in Crimea, and sabotaging fuel depots inside Russia since.