"Instance" refers to a copy which has entities created from Prefab. If you change the content of the Prefab, that change will also be reflected in the Instance. In the process of generating and arranging the same objects in large quantities, Prefab and Instance make it possible to collectively manage them, so it is one of the most important term in Unity. *See the item of <a href="https://www.gameassetstudio.com/word?index=P#prefab">"Prefab"</a>