I am assuming that you are talking about the importance of peer observations. Many schools have peer observations in place. What this is simple. Teachers pair up and they attend each other classes. The visiting teacher may spend a class session observing the teacher and his or her pedagogical method. After the class, the visiting teacher gives his or her comments - both positive and negative. This is important, because we all have blind spots and can use improvement.
Another type of observation is when the visiting teacher observes the class or students. The purpose of this is to see how the students respond the the teacher. In this way, you can see what works and does not work. In the end, it really is about personal enhancement, that is, becoming a better teacher.
Sometimes one school visits another. This can also be very valuable.