What is exactly access arguments used for in hook_menu? I have read the link : hook_menu

Snippet from the page 


  "access callback": A function returning TRUE if the user has access
  rights to this menu item, and FALSE if not. It can also be a boolean
  constant instead of a function, and you can also use numeric values
  (will be cast to boolean). Defaults to user_access() unless a value is
  inherited from the parent menu item; only MENU_DEFAULT_LOCAL_TASK
  items can inherit access callbacks. To use the user_access() default
  callback, you must specify the permission to check as 'access
  arguments' (see below). 
  
  "access arguments": An array of arguments to
  pass to the access callback function, with path component substitution
  as described above. If the access callback is inherited (see above),
  the access arguments will be inherited with it, unless overridden in
  the child menu item.


But Still unclear about what access arguments are actually used for ? 
Are the access arguments the permissions ?
Access arguments is the key for an array which contains the user permission. This means that current user must have this permission to access this page. 

We can use already defined user permision or can create new permission for our menu item.

If you go to permission page (Administer >> User Management >> Permissions), you can see the list of string you might use for access arguments. 

If you want to create new permission for your menu item, you can implement hook_permission in your module.