What is a ScriptableObject?

The short version

A ScriptableObject is a Unity object that holds data and lives as an asset file in your project, rather than on a GameObject in a scene. You create, name and edit it in the inspector like any other asset.

It suits player stats, game settings, an inventory definition or a difficulty curve: data authored in the editor and read from anywhere in your game.

vs. MonoBehaviour

A MonoBehaviour is a script attached to a GameObject. A ScriptableObject is its counterpart for pure data.

• MonoBehaviour lives on a GameObject, inside a scene or prefab. It has Update, Start, a transform, and so on.
• ScriptableObject lives as a standalone .asset file in your Project window. No GameObject, no scene, no per-frame loop. Just fields.

A ScriptableObject is a single shared asset: every script referencing it reads the same data, with no copies to keep in sync.

Making one

Three steps, all standard Unity:

1. Write a class that inherits ScriptableObject.
2. Add [CreateAssetMenu] so it shows up in the Create menu.
3. Right-click in the Project window and create an instance. Its fields appear in the inspector, ready to edit.

using UnityEngine;

[CreateAssetMenu(menuName = "Player Data")]
public class PlayerData : ScriptableObject
{
    public int gold;
    public int level = 1;
}

That is a plain ScriptableObject. The Persistent Asset example is identical, apart from the base class it inherits.

The catch

A ScriptableObject authors data, but it does not save it. In a built game, a change made while playing lives in memory only and is gone when the game closes: the authored values load fresh on every launch.

Persistent Asset adds the missing piece: inherit PersistentScriptableObject instead of ScriptableObject, and the data is saved and restored between sessions.