Help identifying this rear-wheel part (photo)
It is indeed a broken rear axle.
If you nave no proper tools (freewheel/cassette remover, cone wrench 15mm, wrench 17mm, new QR axle, 2 rings of new bearings), get it to an LBS to replace it.
It's also recommended to check the wheel bearings cups for defects, it maybe a good time to replace the wheel - all depends on the shape of other parts, and the cost to bring it to proper state.