These very simple samples demonstrate the basic elements of the Entities API.
The Data Oriented part is done with Unity ECS (DOTS) and is always executed inside a subscene to hold everything in (a world to manage and not share with the objects). These scenes hold an Entity calles Execute which tells which systems will be executed.
The sample contains a single cube with a smaller child cube. The larger cube has a RotationSpeedAuthoring MonoBehavior, which adds a RotationSpeed IComponentData to the entity in baking.
At runtime, the RotationSpeedSystem spins all entities having the RotationSpeed component (in this case, just the single parent cube).
This sample is the same as "MainThread", except the RotationSpeedSystem now uses a job (an IJobEntity) to spin the cube instead of doing so directly on the main thread.
This sample is like "MainThread", except the RotationSpeedSystem now uses an aspect to move the cube up and down.
The sample contains a single non-rendered entity with a Spawner component that references a cube prefab.
At runtime, the SpawnSystem spawns many instances of the cube prefab and places the instances at random positions. The RotationSpeedSystem makes the cubes rotate and fall. The FallAndDestroySystem destroys cubes when they fall below y coord 0. Once all cubes are destroyed, SpawnSystem will spawn more cubes.