What is the reload function for? Any documentation i can read on this?

If you chain multiple actions that alter the user object you need to reload the user object with each action as they won't have the changes made from the previous action.

To expand on this further CB Auto Actions, when possible, will use the user object sent by the trigger (if one exists) and pass it to its actions. This is typically the behavior you want except in the case of chaining user object changes in which case you need to reload the user object.

What does the reference do? Can't seem to find the documents on this..

CB Auto Actions can work with reference variables, but it has to be told in advance which variables of the trigger are references. For an explanation of references in PHP please see the below.

php.net/manual/en/language.references.php

This can be useful to counter the above chain-ability. For example if you are using a single trigger and know what variable you need as a reference (e.g. user object) then you don't need to reload the user as the reference will be modified. This requires knowing what the exact variables of a trigger are though.