Minecraft – command to query how many chunks make up a given world? (v1.15.2)

One approach to solving this problem is to run your world from a RAM disk, with regular (and atomic) pushes to disk. I implemented this on my SMP server (Linux guide here) for performance reasons, but as a side effect it should at the very least make world corruption much, much less likely to happen, especially using rsync to push the world to disk (rsync is about as atomic as you can get with file operations, so even a power loss during the push to disk shouldn't cause any problems).

With this approach implemented, a power loss will at worst cost you 15 minutes of work in your world (if you use the 15-minute scheduled push I do in the guide), which is a far cry less bothersome than world corruption (which has affected my SMP world twice before I implemented the RAM disk approach).

Straight from the Minecraft Wiki:

Entities encompass all dynamic, moving objects throughout the Minecraft world.

The wiki entry on the debug screen has more info (paraphrased):

+------------------------------------------------------------------+
| Name           | Legend                                          |
+----------------+-------------------------------------------------+
| E (second row) | Number of rendered entities over total entities |
+----------------+-------------------------------------------------+

So, you are partially correct:

• Entities are mobs (friendly or hostile), items, and quite a few more.
• The 'number rendered' is the number of rendered entities