A task is any system activity that takes time to complete; for example, VM migration or powering a VM on/off. Tasks can be started manually or scheduled using a built-in scheduler.
Tasks for a particular inventory object can be viewed under the Tasks & Events tab. Detailed information about the tasks can be viewed in the Details pane. A list of recent tasks can be viewed under Recent Tasks on the status bar as shown in the following screenshot:
Certain tasks can be canceled by right-clicking on them in the Recent Tasks list and choosing Cancel. This option cancels only the running task. In the case of a scheduled or recurring task, it needs to be edited or deleted from the Scheduled Task pane.
You can cancel the following tasks:
Connecting to a host
Cloning a virtual machine
Deploying a virtual machine
Migrating a powered-off virtual machine (only when the source disks have not been deleted)
If vSphere uses virtual services, the following tasks can also be canceled...