Hi Rajesh,
Incident Management focusses in allowing the user to work when something is impeding his work. Speed and communication is essential. Workarounds are useful. Incidents sometimes are waiting on a Problem or Change.
Problem Management focusses in resolving root causes. Problems sometimes are waiting on a Change.
Change Management (aka Request for Change or RfC) focusses on keeping the CMDB up to date, and managing any modifications via risk acceptance and documentation. Change sometimes are waiting on a Release or a Project... Changes typically take less than a week to implement and are IT mostly centric. Typically a group of experts (Change Advisory Board, or CAB) meets each week to discuss, approve and plan the Changes. The output is an improvement in stability and reliability of the IT.
Demand Management is similar to Change Managemnt, without the CMDB/IT focus. The idea is to analyze any demand to decide if it should be considered, what are the risks/costs/benefits, and allows to forward the demand into a new Change, Project, Defect or Enhancement Request.
Project Management is about large changes affecting the enterprise. Projects typically take more than two weeks to implement. It's the realm of Project Manager. Portfolio Management is for those PMO who manage a whole bundle of projects. Projects and their budget are often validated at the top management level (Cxx).
Release Management is about grouping RfC in a single change. Like a new software version, including lots of different enhancements in one big update.
This very useful image shows the relations between the types of tasks.
Example: User's laptop is broken...
Incident Management: Service Desk will lend a loaner laptop for a few days, allowing the caller to continue to work.
Change Management: Service Desk will de-assign former laptop, configure a new one from stock, order a new laptop to keep the inventory, have the new laptop assigned to caller.
Problem Management: Investigate with vendor why 10 recent laptops have their hard-drive suddenly dropping dead in less than one month. Possibly deciding to stop using that model and recalling all laptops with the same HD model.
