Online chess has good points and bad points. Let's start with the bad points.
* It can be a terrible time sink. Be careful of too many late (k)nights!
* Playing on a screen rather than over the board takes some getting used to. Have you ever played chess against your computer? It feels much the same to begin with.
* You can pick up bad habits. Most online chess is blitz chess (or faster), making it difficult to play carefully. If that makes its way to your over the board play, you won't be very popular with your team captain.
* There are quite a few cheats around. I'm not sure I've run into any, but there are some unscrupulous players out there who will put your moves into their chess computer and play their computer's moves against you. You might be playing against Fritz (or another powerful chess engine) without realising!
In my view the good points outweigh the bad:
* It can be tremendous fun.
* Unlike playing against a computer, your opponents will make mistakes.
* You can get lots of practice for a new opening in a short space of time.
* If you find yourself running out of time in over the board play, online play may help you learn to play a little faster (when required).
* Play on the right websites, and you could find yourself playing against a GM.
* If you don't like the tight time controls, several sites allow 'non-live' play. It works in a similar way to correspondence chess.
There are lots of places to play chess online. One of my favourites is Chess.com. You can join for free (or get paid membership for extra benefits and the removal of adverts). The site allows both live and non-live play, and you can search for opponents based on their rating. The site also has lots of extra learning resources including puzzles, tutorials, articles and videos. At the time of writing Chess.com has 6,819,325 members, ranging from complete beginners to Grand Masters. They have team matches (I'm a member of two teams), tournaments, and an active online community. They've also made most of this available via their (free) iPhone and Android apps.