The first clause of ISO 9001 2015 is scope. Two things have been told in this clause. One is which kind of company needs this quality management system standard and why it is need? If we say who needs then the answer is any kind and any size of organization can adopt this standard

If we go why needs then two answers will come there first of all: If any company wants to demonstrate its ability to consistently provide products and services that meet customer and applicable statutory and regulatory requirements and secondly if any organization wants to enhance customer satisfaction through the effective application of the system, including processes for improvement of the system and the assurance of conformity to customer and applicable statutory and regulatory requirements.

In the clause 2 and 3 there is references of ISO 9000:2015 for normative reference, terms and definitions. So, there is no more to learn from those two clauses. However to know more about clause number 4 you may visit this post