hook_user_insert() vs hook_user() can someone please explain the difference between 

hook_user_insert() and

hook_user() with $op='insert'

i mean is hook_user with $op='$edit' is invoked after a user create an account??

cos i am trying to get some custom field values when a user create a new account.
i used this code for testing:

function myModule_user($op, &amp;$edit, &amp;$account, $category = NULL) {
  if ($op == 'insert' ){
    dpm($edit)
  }
}


and it don't return nothing after creating a new user account.
The simple answer is that hook_user is for Drupal 6 and hook_user_insert is for Drupal 7.

Most (all?) of the API functions in Drupal 6 and earlier that accepted an $op parameter got split out into individual functions in Drupal 7.  This happened with hook_block, hook_nodeapi, and some others.

For Drupal 7, the full set of user hooks is described at user.api.php.