Professional poker players are more dedicated and well-focused on the game or should we say that they have an advantage when it comes to experience. Anyone could play poker but not anyone could be professional in it. It needs a further understanding of how to deal with the risks of this game and having a sense of responsibility at the same time. People prefer poker over other gambling games because its risk is more manageable than others.
Professional means that they get money from the poker. It becomes a job. Of course they well-focused and more experienced players. And they get advantage the same as in any other job - their experience helps to analyze situation on the table fast and predict the next steps of the opponents. When the common player need time to think what to do, the professional make his bet instantly. The most interesting situation is when several professionals plays. In such situation they begin to think. When i understood how it works i stopped play poker - just sometimes $5-10 for fun.