☆Fun fact: "Good" advertisers can pay the ABP developer to whitelist their ads.
By default Adblock Plus allows certain ads (for a fee) but you can disable the "non-intrusive" ads in the settings. It's the nonsense, deceptive and/or intrusive ads that get blocked by default. There are also multiple other ad blockers available and a few have a fairly large user base. ABP is just the oldest and most well known.
On another note, playing devils advocate, you can manually whitelist and blacklist ads in ABP. Most of the internet depends on ad revenue. If your favorite website has non-intrusive ads then consider not blocking them or just blacklist those that are annoying.