Why are the names so similar?
Long, long ago, somebody (not us) created a Firefox add-on called Adblock. Later on, another team created a different Firefox add-on and adopted the name Adblock Plus (ABP).
When Google Chrome came along, the Adblock Plus team wasn't interested in supporting the new browser. Michael Gundlach created an ad blocking extension he called, naturally enough, AdBlock for Chrome. It went on to become the most popular Chrome extension. Then the Adblock Plus team decided to support Chrome after all. Over time, both AdBlock and ABP added support for additional browsers and platforms. And that's why the two most popular ad blockers have such similar names. Aren't you glad you asked?