Most cars have a sway bay in the front and rear. It ties the two sides of the suspension together to help control body roll during cornering. The sway bar is connected to the rest of the suspension by a link at each end with ball joints in them. The links are a part that fails more frequently than other suspension parts, but they’re not that expensive, so it’s not too big a deal.
Someone had taken it upon themselves to actually repair the rear sway bar links on this car, putting four screws in where the plastic inner part comes through the metal outside. The top is repaired, the bottom is what they normally look like. It seems to be working fine, but I wouldn’t recommend doing this. Just replace the links.