What is ISO Certificate?

ISO 9001:2015 is an international standard dedicated to Quality Management Systems (QMS). It outlines a framework for improving quality and a vocabulary of understanding for any organization looking to provide products and services that consistently meet the requirements and expectations of customers and other relevant interested parties in the most efficient manner possible.i The QMS is the aggregate of all the processes, resources, assets, and cultural values that support the goal of customer satisfaction and organizational efficiency. First published in 1987, the latest iteration (ISO 9001:2015) replaces ISO 9001:2008.
ISO 9001:2015 doesn’t dictate what an organization’s objectives should be or how to achieve them. In other words, it doesn't tell anyone how to run their business. It's a flexible standard that allows each organization to define for itself what its objectives and adherence to the standard ought to be. ISO 9001:2015 defines the guiding principles that can be used to create efficiencies by aligning and streamlining processes throughout the organization, in an effort to bring down costs, create new opportunities, meet regulatory requirements, and help organizations expand into new markets in which clients demand ISO 9001 certification (the last of which is increasingly crucial for businesses working in or with the public sector or serving as suppliers in automotive or private OEM (Original Equipment Manufacturer) scenarios).

WHAT DOES ISO 9001 CERTIFICATION MEAN?

If an organization bills themselves as "ISO 9001 Certified," this means the organization has met the requirements designated under ISO 9001 (which you can read in full here). ISO 9001 requires organizations to define and follow a quality management system that is both appropriate and effective while also requiring them to identify areas for improvement and take action toward those improvements.
As a result, it's typically understood that an organization claiming ISO 9001 certification is an organization with products and services that meet quality standards.