On-the-job training is pre-job training. For example, your job is programming, and your job training should be java training and Android training. Professional knowledge generally refers to the majors I have studied in the university and the industry knowledge I am engaged in. For example, java knowledge refers to my programming expertise, and skill training generally means that I have not learned this skill to train. Just like I am a math teacher, I want to teach Chinese and train Chinese. Chinese is skill training. These are all my understandings, but I