You can read about this in Chapter 18. There are three bull fighters - Belmonte, Marcial and Romero. Belmonte was very good, but he was past his prime. Although he was famous, the people expected him to be more than very good - they expected him to be perfect, which he was not. He worked close to the bull, but in his own terrain. If a bull fighter enters the bull's terrain, he can be killed because he is too close to the bull. When he was a younger man, Belmonte always worked in the bull's terrain but in this bull fight, he stays in his own terrain. This is not exciting and the crowd is not pleased.
Marcial's performance was also mediocre. Belmonte did not worry about competing with Marcial because he, too, was past his prime.
Romero was young and had a unique talent for bull fighting. He was able to use his cape skillfully to entice the bull, and he moved with grace. He was often in the bull's terrain. One of the bulls he was fighting could not see well, and the crowd wanted this bull removed, but the president refused. Because the bull could not see well, he could not see the colors of the cape, so Romero had to get very, very close to him. Romero took his time and played with the bull, the bull thought Romero had given up, so he charged and Romero immediately put his cape out in front of the bull in a skillfull move before Romero threw his muleta over the bull's head to blind him.