Most players have been using programs like this (YVD and KCVDS included), which you had to download and update yourself, then look online for opponents. Routers make this a hassle, as you have to bypass your firewall and IP address. However, the "invention" of browser-based dueling outlets made things very convenient, and now we have one that is (mostly) stable and easy to use.
Online dueling is great for many reasons. Not only can you duel with a friend from a distance, but you can duel players from anywhere in the world. This lets you get practice against a variety of decks in your free time, and prepare yourself for any tournament you may go to. You can strengthen the way you play your own deck, or try out any other type of deck.
Dueling online isn't a sure fire way to make yourself "America's Next Top Duelist" (patent pending), as winning at this game requires more than just cards and knowledge. You need to be able to read your opponent and know how to bluff, which is nearly impossible when facing a computer screen. The best thing you can do is learn the ins and outs of your own deck while also learning what other decks can do and how to counter them, then use that experience against friends or players at local tournaments and work on your psychological game.
If you come across CrashLove37, hit me up for a game, and remember; Online experience+Real life experience=gg.
...that's a terrible way to end an article.......um......Peace Out, Bitches!