How can I change the status of tasks and events to "Completed"?

How can I change the status of tasks and events to "Completed"?

All the tasks and events that are not yet over, are listed under the Open Activities Related List and all the activities that are over, are listed under the Closed Activities Related List.

Tasks refers to a piece of work that is required to be done within a specific time frame. So, when a task is completed, you need to manually edit the task to change the Status as Completed. All the tasks with the Completed status, are listed under Closed Activities.

Event refers to any activity that happens at a specified time and place. So, when an event is over, it automatically gets listed in the Closed Activities.