Unity ECS, Jobs and Burst

Platforms and SDKs Games and XR

Official docs Learn it on your Mac

Official docs outline

5 sections

Entities package
Entities, components and systems.
C# Job System
IJob, scheduling and safety.
Burst compiler
Burst compilation.
Collections
NativeContainers.
Addressables
Addressable assets.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.