LOL are you asking the difference because im pretty sure they both mean the same thing or do you just not know in general what they mean? For definitions you can just Google it like alexjames said up top
I think to know whether to scrape or scrub, it really depends on where the leads are and how easy they will be to remove. For instance, if they have been on there a while, you may want to scrape:
but if they are relatively new, a good scrub (with elbow grease) will do the trick:
Scrubbing = Eliminating invalid, duplicate and unqualified leads. Common practice in most lead-gen industries and widely accepted method of mainting quality.