ISO 9001 vs ISO 14001

The main difference is that ISO 9001 is focused on Quality management system while IS0 14001 on Environmental management system. For being more specific ISO 9001 is a Quality Management System (QMS) which gives organizations a systematic approach for meeting customer objectives (providing consistent quality) while ISO 14001 is an Environmental Management System (EMS) which provides a system for measuring and improving an organization's environmental impact.

The structure of the two standard is similar , in fact there is also a table to reference clause of ISO 9001 to ISO 14001 ones. An organization can be certified vs both standards and can also pursue the integration of the two systems as well.  They share several requirements and the goal of contiual improvement, but also differ in their approach and degree of prescription. One important difference between ISO 14001 and other ISO standards is that an organization can self-declare their compliance.

There are many other differences in the theorical level, like: there are no normative references defined in 14001, 9001 asks for a Quality Manual but 14001 doesn't, 9001 requires 6 documented procedures whereas 14001 requires only one documented procedure, 14001 requires to document Responsibilities & Authorities but 9001 doesn't require them to be documented anyway, exclusions are permitted in 9001 but not in 14001, while 14001 requires only 6 or 7 records, there are as many as 21 required to be maintained by ISO 9001, 9001 exclusively focuses on enhancing Customer Satisfaction while the 14001 is aimed at minimizing harmful effects of our activities.