Surprise and The Drop-what's the difference
Surprise is a lesser version of The Drop it offers +2 to hit and damage and represents situations when someone is prepared for combat but may not know exactly where the attack is coming from.
The Drop bonus is only gained when the target is completely unaware that combat is happening.
Example If Big Bopper is fighting random thug and Transparent sneaks up behind the thug invisibly she would get the surprise bonus. If Big Bopper would have stuck to the plan and let Transparent sneak up on the thug first before he was aware of any enemies she would have had The Drop.