People leave projects, leave the company or, maybe because you misspelled a name, never really existed in the first place. In all these cases, you may need to delete the resource.
Actual work values are deleted
Duration could change
As you remove resources from a task, Project might change the durations (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) for the task as remaining work is redistributed to any resources remaining on the task.
If you don't want the durations to change, turn off effort-driven scheduling (effort-driven scheduling: The default method of scheduling in Project; the duration of a task shortens or lengthens as resources are added or removed from a task, while the amount of effort necessary to complete a task remains unchanged.) for the task.In the Gantt Chart, double-click the task, click the Advanced tab, then select Effort Driven (automatically scheduled tasks (automatically scheduled task: This type of task is scheduled using Project's scheduling engine, taking into account task constraints, dependencies, project calendars, and resource calendars.) only). Learn more about effort driven scheduling.
Costs could change
When you remove a resource from a task, Project deletes any actual costs associated with the resource.
To keep the actual costs for the task, set the remaining work for the resource to zero before removing the resource. In the Resource Usage view, double-click the resource’s name, then in the Assignment Information dialog box, set Remaining Work to 0 (zero).
Deleting enterprise resource