Texas Holdum is a very popular poker game. To play, you get dealt 2 cards. Then the dealer flops over 3 cards, turns over the next one, and then comes the final card (river card) that will make or break your hand if your still in the game. Last but not least you will have a showdown to see who has the best hand.
There is a betting sequence between each round where you have a few choices called folding, raising or re-raising. You can bet up to 4 times in limit holdum. In no-limit that doesn't apply because you can raise as many times as you get re-raised until you are all-in or fold your hand.
Bluffing is something that is not suggested nor does it make any real sense in limit holdum. In no limit it will cost you more in the long run until you get a name about how you play which that takes a bit of time when playing online.
Some great places to play live Texas Hold'um online include: Party Poker, ParadisePoker and Pacific Poker.