Scenes and GameObjects

How it works and why

A scene is a saved composition of GameObjects. A GameObject is a container for components; the components provide behavior or data such as a Transform, a MeshRenderer, a Collider or your MonoBehaviour. A GameObject by itself does not render a model or simulate physics. The Transform expresses its position, rotation and scale.

Use several scenes when you want clear loading boundaries (menu, level, results), not because each prefab needs a separate scene. An additive scene lets you keep multiple scenes loaded at once, useful for shared lighting or large worlds.

Example you can try

using UnityEngine;
using UnityEngine.SceneManagement;

public sealed class LevelLoader : MonoBehaviour
{
    // The scene must be included in the active build profile.
    public void StartGame() => SceneManager.LoadScene("Game");
}

When to use it and what can go wrong

When to use it: Separate boot/menu/game scenes when they have different lifetimes. Put reusable entities in prefabs. Pitfall: A scene name that works in the Editor can fail in a build if that scene was not included. Avoid hard-coded scene indices when reordering build scenes.

Try it: Create a Menu and Game scene, add both to the build’s scene list and use a UI Button to call StartGame().

Further reading and official references