Udon and Unity have built-in events that are automatically called if you include them in your scripts. For example, the
Start() event runs once for every script, and the
Update() event runs once per frame. When you're writing Udon scripts, it's helpful to know which of these events happen first.
Unity provides an (incomplete) list of built-in events, many of which are also available in VRChat. https://docs.unity3d.com/2019.4/Documentation/Manual/ExecutionOrder.html
The following diagram shows the execution order of the most important events available in Udon and Unity.
Unity and VRChat updates may change the event execution order depicted above. Not all events are listed, and some events may be executed in a different order depending on circumstances (being an object's owner, joining a world late, etc.)