The reasons to play online poker are numerous, listed here are some of the most important ones.
It allows YOU to play when YOU want to You can play when it is convenient for YOU (after work, in the morning, at night, in the middle of the night, after the kids go to bed, whenever). Games are available all day and all night 24/7. You are playing against opponents from around the world, so there are always a large number of players to compete with.
YOU don't have to travel to a poker room The games are right there on your computer. This is really helpful if you live any distance from a poker room. Especially with the price of gas now, this can save YOU an awful lot of money.
YOU have a much larger selection of games Online poker offers you many different games such as Hold'em, Stud, and Omaha. Unlike a brick and mortar (B&M) room, you don't have to wait that long, if at all, to find a table to play at.
YOU can play at much lower limits (even micro limits) The limits at most online poker rooms are much lower than at B&M rooms. This allows you to have a much smaller bankroll to start with. In fact, the minimum buy in for a B&M room can be a reasonable starting bankroll for a new player at an online poker room.
More tournaments are available There are far more tournaments available at the online poker rooms than there are at B&M rooms. The buy ins are a lot less and there are more players. Online rooms also offer sit & go tournaments that are not available at a B&M room. Another type of tournament that online poker rooms offer is the "Freeroll", which allows YOU to play for prize pools without investing any money. YOU can leave when YOU want to With no consideration for the drive home or for the time it took you to get to the poker room, YOU can leave when YOU want to.
Sign up is easy and secure You can sign up for many online poker rooms, it is easy and secure. Just download their software and open your account.
It is less intimidating for new players If you are a new player, you would be at a loss to know all the poker etiquette required at a B&M room. In online poker, this is not a problem as the rules are all posted and many of the things that you need to remember are done for you automatically. Such as posting your blinds, knowing when it is your turn to bet, not letting you bet out of turn, etc. Managing YOUR bankroll is easier As the amount of money that you have on account in a room is always available, you can see if you are winning or loosing and can decide what limits YOU want to play at.
YOU have a huge selection of card rooms There are literally hundreds of card rooms online and the selection is very large. You can find rooms that are pleasant for YOU to play at, or more profitable, or that offer the games YOU want.
Table selection is much easier than at a B&M room In a B&M room, you go in, put your name on a list, and take the first seat that comes up. This is not the case in an online room. In an online room YOU can pick your table by the percentage of players seeing the flop, average pot, number of hands dealt per hour or many other criteria. Then you can go watch the play at the table before you sit in.
Calculating YOUR pot odds is easier As the amount of money in the pot is always posted, it is quite simple to calculate the odds that the pot is offering on any one bet.
Play on more than one table/room at a time Online poker allows you to play at one or more table(s), simultaneously. On the other hand, you can play at several different rooms/sites at the same time. Ease of taking notes on different players Most online rooms give you the ability to make notes on your opponents, which will show up every time you play them.
In summary online poker offers you the most convenient and comfortable way to play poker. Sign up for a room and join the thousands of us poker players.
Good luck.

About the Author
Authored by: Robert Myer, Webmaster of Beginner's Online Poker Guide, as well as a poker player for over 20 years.