When talking about file systems it doesn’t hurt to be familiar with the following terminology.
Disk
A permanent storage medium of a certain size. A disk also has a sector or block size, which is the minimum unit that the disk can read or write. The block size of most modern hard disks is 512 bytes.
Block
The smallest unit writable by a disk or file system. Everything a file system does is composed of operations done on blocks. A file system block is always the same size as, or larger (in integer multiples) than the disk block size.
Partition
Any subset of the total number of blocks on a disk. A disk can therefore have several partitions.
Volume
The name we give to a collection of blocks on some storage medium (i.e., disk). That is, a volume may be all of the blocks on a single disk, some portion of the total number of blocks on a disk, or it may span multiple disks and be all of the blocks on several disks.
The term volume is used to refer to a disk or partition that has been inititialized with a file system.
Superblock
The area of a volume where a file system stores its critical volumewide information. A superblock usually contains information such as: - how large a volume is, - the name of the volume, - and so on.
Metadata
A general term refering to information that is about something but not directly part of it. For example the size of a file is very important information about a file, but it is not part of the data in the file.
Journaling
A method of ensuring the correctness of file system metadata even in the presence of power failures or unexpected reboots.
I-node
The place where a file system stores all the necessary meta data about a file and any other data associated with the file. The term i-node is historical and originated in Unix. An i-node is also known as a file control block (FCB) or file record.
Extent
A starting block number and a length of successive blocks on a disk. For example an extent might start at block 1000 and continue for 150 blocks. Extents are always contiguous. Extents are also known as block runs
Attribute
A name (as a text string) and value associated with the name. The value may have a defined type (string, integer, etc.), or it may just be arbitrary data.