It seems like everyone is pretty much saying the same (and correct) thing, so allow me to add my voice.
White hat SEO refers to all practices that fall within Google guidelines, they are considered acceptable by Google because the end user benefits in some way from these practices. Black hat practices refer to techniques that can be inconvenient to the user (hence, the reason why they are not allowed by Google) Websites that practice black hat may benefit in the short run, but if Google catches this website, they will be blacklisted and removed from the SERP by Google.