What's great about this is that you can do it anytime you please. Sure, brick and mortar casinos are usually open most anytime but it's not always convenient to go. Most places don't even have a casino nearby so when you can go it can turn into a major vacation instead of a fun-filled day of winning money.
The best way to know which online casinos to use is to browse a site that explains more about the ins and outs of online gambling. You can find out which casinos are the best, which have the highest payouts and even the legalities of gambling. Besides, what do you have to lose?