Requirement is the demand or the expectation of the person who want to achieve something from the given task. Requirement is the important desire given to fulfil the expectation of any project.
Without the gathering the proper requirements the person will not be able to find what exactly is expected with the project outcome. Basically requirement is the path to success of any project.
Requirements enables to meet the goals of the project.
Difference between requirements and need is that need is the desire of any person which is mandatory or must in nature however the requirements are the required tasks to achieve the goals or needs. A need is the goal or the success to be achieved and requirements is the roadmap to achieve the needs. Requirements are dynamic in nature which can be changed according to the nature of the product however the need is static in nature which is the end result of the project.
Customer need is the expectation of the customer from any product however the requirements are the various steps to meet the set expectations of the client from the product.