-*btrfstune* is used to tune various btrfs filesystem parameters,you can
-enable/disable some extended features for btrfs.
+*btrfstune* can be used to enable, disable, or set various filesystem
+parameters. The filesystem must be unmounted.
+
+The common usecase is to enable features that were not enabled at mkfs time.
+Please make sure that you have kernel support for the features. You can find a
+complete list of features and kernel version of their introduction at
+https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature . Also, the
+manual page `mkfs.btrfs`(8) contains more details about the features.
+
+Some of the features could be also enabled on a mounted filesystem by other
+means. Please refer to the 'FILESYSTEM FEATURES' in `btrfs`(5).