CIPD Level 3 is Foundation course and made easy for beginners. It provides a base knowledge for people who have little experience in the practical field of Human resources or learning and development.
CIPD Level 5 is intermediate level and builds on the knowledge of foundation level. Students might take direct entry into Level 5 as well provided they have a degree in human resources or learning and development or have worked in a managerial position in these fields.
CIPD Level 7 is an advanced course and need in-depth knowledge in the field of human resource or learning and development. It is equivalent to post-graduation degree so demands a lot of pre-requisite knowledge. If you have not cleared the intermediate level you at least have to have a graduation degree in human resources or have plenty of experience in the practical field.