What happens with $q.all() when some calls work and others fail?

I have the following code:

    var entityIdColumn = $scope.entityType.toLowerCase() + 'Id';
    var requests = $scope.grid.data
      .filter(function (rowData, i) {
          return !angular.equals(rowData, $scope.grid.backup[i]);
      })
      .map(function (rowData, i) {
          var entityId = rowData[entityIdColumn];
          return $http.put('/api/' + $scope.entityType + '/' + entityId, rowData);
      });
    $q.all(requests).then(function (allResponses) {
        //if all the requests succeeded, this will be called, and $q.all will get an
        //array of all their responses.
        console.log(allResponses[0].data);
    }, function (error) {
        //This will be called if $q.all finds any of the requests erroring.
        var abc = error;
        var def = 99;
    });

When all of the $http calls work then the allResponses array is filled with data.

When one fails the it's my understanding that the second function will be called and the error variable given details.

However can someone help explain to me what happens if some of the responses work and others fail?