The tables won't always look the same. They're a lot classier in the Bellagio than they are in your neighbor's club house. Sometimes the tables you play poker on aren't even real, with virtual casinos like Caesars Online becoming more and more popular. However, the important thing about the table isn't how it looks. It's how it behaves. Believe it or not, the way your table behaves will change constantly throughout the night. The reason for this is what's referred to as position.
There are three categories of position that you can be in, and these positions are all in reference to how close you are to the dealer button and in what direction. The plays you can make are vastly different from position to position, and moves that would be downright idiotic in early position are brilliant in late position.
Late position is being "on the button" (the dealer button is in front of you) or being in one of the two seats to the right of the dealer button. Early position is small blind, big blind, and the position to the left of big blind (the player who will be big blind next round). The four additional players at the table are all in "mid" position.
The most basic explanation is that you can take a lot more risks in late position. The reason for this is that you have already seen the actions taken by most players (depending on your position, you have seen five to seven players make their choice). Since you know whether or not these players are going to fold, call, or raise, you can effectively eliminate risk that would otherwise be a part of a call or raise that you want to make. By the same token, those in early position are left blind and are in greater risk, so caution is wise.