All learners make mistakes. As someone has said: "You can't learn without goofing". Whether you are learning how to ride a bicycle, how to fly a kite or learn a language, everyone does make mistakes.An error is an incorrect form and a sure indication that the learner has not mastered the core of the selective topic in a learning process.Errors offer an opportunity for the teachers to understand students thinking or thought processes since they are a window to children's thinking. Errors are necessary for the learning process to give insight into children's thinking. It helps the teacher to be aware of learners' learning styles and to cater to them according to their needs.Making an error cannot be just due to negligence and carelessness. It may be so that students are thinking about it in a different manner other than what is the right process.To understand this, a teacher should analyze what mistake the students are doing, how the mistake is generated, and where exactly they tend to make mistakes.?Hence, it is clear that errors offer an opportunity for the teachers to understand students thinking.