Table image is a huge part of poker. What you are communicating at the table with your play is as important as what you are verbally communicating, and both you and your opponents can use this as an advantage. Your table image is the general perception of your style of play at the table. Players will generally fall into being weak-tight, tight-aggressive, or loose aggressive.
There are certain things you can do to use your table image to your own advantage. If you are a loose player seeing a lot of flops, be sure to make your opponents aware of it, as it is how you get paid off. When you pick up a premium hand, and you play it much in the same way, then you are going to maximize your profits. Playing like this will often make your opponents question decisions they make against you.
You can also do the same thing as a tight player. If you have only been betting out pre-flop with premium hands, then people are going to be less likely to call you. Picking up the blinds is an important element of the game, and if you get a caller, often a continuation betbluffs. Nothing will make your opponent want to cringe more than you showing him you outplayed him with a worse hand. Usually it will cause a player to get tilted and start doubting their own play. What will cause them even more frustration is when they think they have caught you in a bluff a few hands later, and you turn over the nuts.
Whether you are a tight aggressive player, or a loose aggressive maniac, there are certain things you can do to enhance your table image and use it against your opponents. With less and less fish finding there way to online poker, any little thing you can do to give yourself an edge is crucial.