unity "[]" tag Attributes

All Attributes, below left of the page
https://docs.unity3d.com/ScriptReference/ExecuteInEditMode.html

[CanEditMultipleObjects] // object editor can be more
public class Collider2DEditor: Editor {}

[SerializeField] // serialize Private property
private Emitter _emitter;

[ExecuteInEditMode] // make all instances of the script is executed in edit mode.
public class Test: MonoBehaviour