{% if currentUser.isInGroup('groupHandle') %}

{{ currentUser.getGroups() }}

{{ currentUser.can('permissionName') }}

//get the current user from craft
$user = Craft::$app->getUser();

//check if the current user has permission to edit certain entries
$user->getIdentity()->can('editEntries: 27')

//check if user is in group
$user->getIdentity()->isInGroup('specialGroupHandle'));

//get the current user from craft
$user = craft()->userSession->getUser();

//check if the current user has permission to edit certain entries
$checkPerms = $user->can('editEntries: 27');