Cost resources provide an easy way of applying miscellaneous or multiple costs to a task, like airfare and dining— in addition to the more commonly applied costs like people's salaries or per-use costs, such as consultant fees. Cost resources don't depend upon the amount of work done on tasks. Nor do they depend on any calendars used in the project, as do work resource salaries, or rate costs for material resources, such as computer time and rental machinery. Keep one important thing in mind as you use cost resources: You can reuse same cost resource.
Let's look at this a little more closely since cost resources are created differently than the other costs, and they're applied differently as well: