Btrfs is a new filesystem with extents, writable snapshotting, support for multiple devices and many more features. Btrfs is highly experimental, and THE DISK FORMAT IS NOT YET FINALIZED. You should say N here unless you are interested in testing Btrfs with non-critical data. To compile this file system support as a module, choose M here. The module will be called btrfs. If unsure, say N.
POSIX Access Control Lists (ACLs) support permissions for users and groups beyond the owner/group/world scheme. To learn more about Access Control Lists, visit the POSIX ACLs for Linux website <http://acl.bestbits.at/>. If you don't know what Access Control Lists are, say N