So, since you seem to know about it, can you explain more to me? I basically used it to block a site that would ask me for a serial number for a product.
A HOSTS file takes URLs and redirects them to the local host. For example, if an ad from "ads.dealnews.com" is sent to any web page you are viewing, and the HOSTS file contains a record for "ads.dealnews.com", then the request is sent to the localhost (your computer) instead of ads.dealnews.com. This, in effect, blocks the content because "ads.dealnews.com" instantly can't be found on the localhost.
Using this type of file can speed up general browsing, because you're not waiting for this content to be loaded from the various sources. I'm no expert, so read more here:
http://winhelp2002.mvps.org/hosts.htmThe only downside I've seen is that I can't watch some videos on some news sites. Their ads are blocked, and the video won't play until the ad plays. Catch 22

HOSTS files are dynamic, so you should update every month or so.