[joeraut]

Yes, exactly. The procedurally generated world is predictable* if you know the world seed -- land forms, structures and items/loot spawn the same way each time. You can specify the seed when creating a world, if you like.

There are certain things that are nondeterministic, such as where mobs spawn (that depends on player position, etc.) or how they behave.

* There may be parts of world generation these days that are nondeterministic even with a known seed; I'm not too up to date with recent world generation changes.

[dokem]

There are a few blocks like bees hive that aren’t fully determined by the seed. That can only be determined within a certain location accuracy the rest is random at runtime when the player enters that area. But the block does persist after that.

[skykooler]

One thing that is theoretically deterministic but not in practice is the location of dungeons. These generate in spaces where there is an appropriately sized gap between the floor and the ceiling. Normally these would be determined solely by the terrain generation (and therefore the seed), but it is possible to push blocks into lazy-loaded chunks before the dungeons have generated yet and force them to generate in different spots.

Video on the topic: https://www.youtube.com/watch?v=9iaU1TvIQqM