A "vocation" is an occupation, usually religious, to which someone is specifically drawn or "called" to perform.
A "vacation," which I am presuming you mean in the context of chess.com, is time spent away from the site when you want to pause your games.
Given that many "Online" (i.e., correspondence-style) games can last months, it is not unusual to expect that you may not be available to play at all times. In such instances, you may choose to go "on vacation." To activate it, you must first make a move in all of your games, then go into your settings (http://www.chess.com/home/echess_settings.html) and, near the bottom of that page, click the checkbox marked "PAUSE MY GAMES." Remember to click on the "Save Preferences" button at the bottom.
As a premium member, you also have the auto-protection from timeout. When one of your "Online" games runs low on time (less than 90 minutes), you will automatically be placed on vacation.
what is vocation and how can i use it?