Definition of a Change (proposal)
A proposal for a change to the work to be done, or to the design may come from either the contractor (as a VOR) or internally from the company/client. The change might lead to an increase or reduction in the cost of the work. It might involve a transfer of scope from one contractor to another, based on management of the interface at the battery limit between them. It might have no direct cost, but be related to a change in technical requirements documentation. It might be due to a change in government legislation.
Whatever the cause, change happens - which is WHY you should plan for it.
A change or change proposal is sometimes also referred to as a variation.