Subbed anime is an anime which still has the original Japanese audio in it usually with fansubs but sometimes subtitled by the company. Dubbed anime is when a company such as FUNimation hires voice actors to dub the anime to make it appeal to a wider audience and help focus on the story rather than read the subtitles.
First in my opinion i prefer dubbed anime, don't get me wrong I love subbed anime, most of the best animes haven't even been dubbed yet such as Shugo Chara and Pandora Hearts, but i prefer to be able to focus on the character development rather than to read the subtitles, and with excellent voice actors like Vic Mignogna and Luci Christian, whiny voices are a thing of the past.(Well almost!)
Most people who hate dubbed anime are people who have a jaded opinion of it, even I can admit that animes like Naruto and Digimon have Terrible dubs, and seeing as Naruto is one of the most popular animes out there people then switch to the subs and never return again.
However company's like 4kids have recently lost most of their business (and rightly so) and so have sold the rights to a lot of animes to FUNimation including the famous Dragon Ball Z.
If you go to any anime discussion board you will most likely find some immature person flaming everybody else about the topic, but to be frank anime is not going to become more mainstream unless it is dubbed, American and European culture isn't just going to suddenly develop an instant admiration for the Japanese language so unless it is dubbed it is not going to appear on our television screens.
Here are some of the best examples of perfectly dubbed anime: Shuffle!
and 
School Rumble Feel free to comment and let me know which you prefer and why.
