Short-run equilibrium output refers to the level of real GDP that occurs when aggregate demand equals short-run aggregate supply, resulting in a stable price level. This situation reflects a balance in the economy where the quantity of goods and services demanded matches the quantity supplied at current prices, although it does not necessarily indicate full employment or optimal resource utilization. In this context, fluctuations in aggregate demand can lead to changes in output and employment levels, as firms respond to shifts in demand by adjusting their production.