Unity Foundations

Core Concepts

GameObjects

GameObjects are the fundamental building blocks in Unity. Every object in a scene -- characters, props, scenery, cameras, lights -- is a GameObject. GameObjects are containers: they cannot function alone and require Components to gain functionality. Every GameObject automatically includes a Transform component that cannot be removed.

Components

Components are the functional pieces of every GameObject. Unity uses a composition-over-inheritance architecture: you build behavior by attaching multiple components to a GameObject rather than inheriting from deep class hierarchies. Each GameObject must have exactly one Transform component. Additional components (Rigidbody, Collider, MeshRenderer, custom MonoBehaviours) define what the object does.

Constraints from the docs:

• Components must reside in the same project as their target GameObject
• Components cannot be sourced from separate projects, unattached scripts, or uninstalled packages

Transforms

The Transform component stores position, rotation, and scale -- each relative to the parent (local coordinates) or to the world origin (world coordinates). Key points from the docs: