The process of identifying and defining the services provided by an IT Organization. The Service Catalog is the cornerstone of a well planned ITIL implemetation.
IT Service Management (ITSM) is a discipline for managing large-scale information technology (IT) systems, philosophically centered on the customer's perspective of IT's contribution to the business. ITSM stands in deliberate contrast to technology-centered approaches to IT management and business interaction. The following represents a characteristic statement from the ITSM literature:
Providers of IT services can no longer afford to focus on technology and their internal organization, they now have to consider the quality of the services they provide and focus on the relationship with customers. No one author, organization, or vendor owns the term "IT Service Management" and the origins of the phrase are unclear.
ITSM is process-focused and in this sense has ties and common interests with the process improvement movement (e.g. TQM, Six Sigma, Business Process Management, CMMI).
The discipline is not concerned with the details of how to use a particular vendor's product, or necessarily with the technical details of the systems under management.
Instead, it focuses on providing a framework to structure IT-related activities and the interactions of IT technical personnel with business customers and users.
For the rest of the Wikipedia entry on the above term, go here.