Difference between `ls -c` and `ls -t`

The attributes as handled by lsattr/chattr on Linux and some of which can be stored by quite a few file systems (ext2/3/4, reiserfs, JFS, OCFS2, btrfs, XFS, nilfs2, hfsplus...) and even queried over CIFS/SMB (when with POSIX extensions) are flags. Just bits than can be turned on or off to disable or enable an attribute (like immutable or archive...). How they are stored is file system specific, but generally as a 16/32/64 bit record in the inode.

The full list of flags is found on Linux native filesystems (ext2/3/4, btrfs...) though not all of the flags apply to all of FS, and for other non-native FS, Linux tries to map them to equivalent features in the corresponding file system. For instance the simmutable flag as stored by OSX on HFS+ file systems is mapped to the corresponding immutable flag in Linux chattr. What flag is supported by what file system is hardly documented at all. Often, reading the kernel source code is the only option.

Extended attributes on the other hand, as set with setfattr or attr on Linux store more than flags. They are attached to a file as well, and are key/value pairs that can be (both key and value) arbitrary arrays of bytes (though with limitation of size on some file systems).

The key can be for instance: system.posix_acl_access or user.rsync.%stat. The system namespace is reserved for the system (you wouldn't change the POSIX ACLs with setfattr, but more with setfacl, POSIX ACLs just happen to be stored as extended attributes at least on some file systems), while the user namespace can be used by applications (here rsync uses it for its --fake-super option, to store information about ownership or permissions when you're not superuser).

Again, how they are stored is filesystem specific. See WikiPedia for more information.

For files, ls -l file shows (among other things) the size of file in bytes, while du -k file shows the space occupied by file on disk (in units of 1 kB = 1024 bytes). Since disk space is allocated in blocks, the size indicated by du -k is always slightly larger than the space indicated by ls -kl (which is the same as ls -l, but in 1 kB units).

For directories, ls -ld dir shows (among other things) the size of the list of filenames (together with a number of attributes) of the files and subdirectories in dir. This is just the list of filenames, not the files' or subdirectories' contents. So this size increases when you add files to dir (even when files are empty), but it stays unchanged when one of the files in dir grows.

However, when you delete files from dir the space from the list is not reclaimed immediately, but rather the entries for deleted files are marked as unused, and are later recycled (this is actually implementation-dependent, but what I described is pretty much the universal behavior these days). That's why you may not see any changes in ls -ld output when you delete files until much later, if ever.

Finally, du -ks dir shows (an estimate of) the space occupied on disk by all files in dir, together with all files in all of dir's subdirectories, in 1 kB = 1024 bytes units. Taking into account the description above, this has no relation whatsoever with the output of ls -kld dir.