Do validations only allow true or false

[joebordes]

business actions are mostly UI oriented, they add a button, link, widget or load some code in the front end while events are backend oriented adding functionality at key points of the execution of the code

if you look at the example a few post above you see that I created a business action to load a custom javascript file in the frontend that is called by the validation process.

So, in short: a presave business action is loading some javascript code to be called in the frontend when the user clicks on the save button