signals act very similar to array with callables. When you use ‘connect’ its similar to add this callable to signal array, and when something triggers it, then signal just make .call(arg) to every callable inside. That means callables called immediately or may called deferred if special flag is used.
So if you have a script that do Node.signal_name.emit() and code after it, connected callables are executed before the code that goes after Node.signal_name.emit() part