In a late betting position like the button, you can watch the other players and gauge how much confidence they have in their hands. The only player actions you can't judge are the mandatory bettors, the small and big blinds. On the other hand, if you have a pair of queens and no one has made a significant raise, you might have the best hand at the table.
It's likely that the person who raised has a better hand, so it's wise to fold on this hand and risk nothing. Someone at the table makes a big raise before betting gets to you. For example, say you're the button and you aren't holding anything significant. The button is the last position to act, and the advantage is that he can see what all the other players have decided to do - bet, call, raise, or fold - before he must make a decision. With each betting round, the button moves around the table and the other positions shift with it. Every other player's position is relative to the button. The dealer button is the most advantageous position to be in. Most popular games today have 9-10 players, and where the players are situated around the table is important.