The signals glossary inside the Profile menu dropdown of the console is a great way learn what the signals mean.
You can also add annotations to the signals, including to custom fields you send. For example, if you send a custom field called 'coupon_code':
you can click 'Add annotation +' and enter a description:
Click "Save" and it saves the annotation along with who updated it and when.
If there are signals that you would like more clarity on, feel free to contact our Support Team.