Glad you asked! ISO.org defines a management system as follows:
“A management system is the way in which an organization manages the inter-related parts of its business in order to achieve its objectives and to create a culture that engages in a continuous cycle of self-evaluation, correction and improvement of operations and processes through heightened employee awareness and management leadership and commitment.”
The two best known management systems are the Quality Management System (QMS) for ISO 9001 and the Information Security Management System (ISMS) for ISO 27001.
Although a management system by itself is not a software tool, it is highly recommended to use some kind of system to structure the required documents and provide an overview.
This is where Instant 27001 comes in.