A ScriptableObject is an asset for storing reusable project data.

using UnityEngine;

[CreateAssetMenu(
    fileName = "NewItem",
    menuName = "Data/Item"
)]
public class ItemData : ScriptableObject
{
    public string itemName;
    public int price;
    public Sprite icon;
}

Good uses:

• weapons
• items
• enemy definitions
• configuration
• base statistics

ScriptableObjects are project/design data, not player save files.