This has been somewhat re-interpreted over the years to say the speed is increasing, which is silly, because it presumably started out at near the speed of light.

What is observed is that the further the source is, the faster it seems to recede. which is why it is argued that space itself is expanding, because the effect otherwise is we appear to be at the center of this expansion.

The original assumption was that the source of this expansion was an initial event, which is slowly being slowed by gravity, so the prediction was the rate would drop off evenly, but what was observed is the rate drops off fairly quickly, for the first 7 billion years, then flattens out. To use a ballistics analogy, it would be like the universe were shot out of a cannon, then after slowing, a rocket motor kicked in.

Yet if we consider what we are actually observing, ie, from our point of view outwards, the rate starts off slowly and builds, eventually going parabolic. Which would be reasonable, if it’s an optical effect, compounding on itself.