It's basically a big lookup table, trading storage for speed. The most noticable effect is that your web pages load faster, because a lot requests for unnecess

It's basically a big lookup table, trading storage for speed. The most noticable effect is that your web pages load faster, because a lot requests for unnecessary data (eg. Facebook in this example) complete immediately. Occasionally you will miss out on a webpage that depends on it. Think uBlock Origin, but not for just your browser but your entire system.