The acceleration of the expansion of the universe is sometimes attributed to “dark energy”, but that’s a placeholder term. We don’t actually know what is doing

The acceleration of the expansion of the universe is sometimes attributed to “dark energy”, but that’s a placeholder term. We don’t actually know what is doing it exactly. We can just see that it seems to be happening. The ‘faster than the speed of light’ thing is only if you measure the rate of divergence of objects at very great distances from each other, tens of billions of light years. At more local scales, such as between our neighbouring galaxies and clusters, the effect is relatively small and negligible compared to gravity.