The Pinan katas (some say it is Ping 'An in Chinese) are very important for beginners. The name Pinan means "Peaceful Mind." This name could be inspired by the Bubishi. In article 1 on the History and Philosophy of White Crane. It says, "Immesurable self-conquests are made possible through a peaceful mind and inner harmony. The strength and resiliency gained from martial art training fosters an inner force whith which one can overcome any opponent and conquer worldly delusion and misery." This attitude is essential in preparing one for training in Hakutsuru.
One theory is that Pinan Shodan and Nidan were created by Bushi Matsumura. Many people say they were originally one kata taught to Matsumura by a Chinese master named Channan (some say that the Chinese pronunciation of this is name is Chiag Nan). They say this Chinese master was a diplomat who resided in Shuri. This is further reinforced by a statement from Soken Sensei that indeed Matsumura got these katas from a man named Channan. Some say that Bushi Matsumura later split the original kata up in two, and called them Channan Sho and Dai, or Channan Shodan and Nidan. Later on, they were renamed Pinan Shodan and Nidan. In some newer Japanese styles, these are called Heian, and the order has been switched.
As for Pinan Sandan, Yondan, and Godan, these were supposedly added to the Shorin-Ryu systems by Itosu. Some say that Itosu created these from a different kata taught to him by the same Chinese Master Channan. Some even go so far to say that Itosu created all five of the Pinan kata from the Channan kata, and that Matsumura had nothing to do with it. Whose information do we trust? The best you can do is to pick the explanation that makes the most sense to you. All of these things are plausible, so you just have to use your best judgement.