The phases of compilation are as follows:
Runtime scripts in folders called Standard Assets, Pro Standard Assets, Plugins.
Editor scripts in folders called Editor that are anywhere inside top-level folders called Standard Assets, Pro Standard Assets and Plugins.
All other scripts that are not inside a folder called Editor.
All remaining scripts
(those that are inside a folder called Editor).
https://docs.unity3d.com/Manual/ScriptCompileOrderFolders.html
