Any module can define actions, and then call actions_execute() to make those actions happen in response to events.
'type': The type of object this action acts upon. Core actions have types 'node', 'user', 'comment', and 'system'.
'label': The human-readable name of the action, which should be passed through the t() function for translation.
'callback': Optional. A function name that will execute the action if the name of the action differs from the function name.
'file': Optional. Relative path to a file from the module's directory that contains the callback function.
Actions Functions that perform an action on a certain system object. Hooks Allow modules to interact with the Backdrop core.