and probably more history than you wanted to know, to boot

• ATA - AT(tm) Attachment. The original standard for the IBM "Advanced Technology" computer. Often used interchangeably with IDE (q.v.) or EIDE though the former is only properly applied to ATA-1 and the latter to ATA-2 & ATA-3 (aka Fast ATA). These specs standardized various PIO modes (q.v.) for transfer protocol up through ATA-2, and DMA modes (q.v.) thereafter. ATA/ATAPI-4 and onward are also called Ultra-ATA or Ultra-DMA (q.v.). Confused yet?
• ATAPI - ATA Packet Interface. Allows removable-storage devices to share the ATA bus, notably moving CD-ROMs off proprietary soundcard headers and onto a standard interface.
• Access time - The complete amount of time required to ready a disk drive for read/write at a new location. Composed of the seek time and the rotational latency (q.v.).
• CHS - Cylinders, heads, & sectors. The addressing scheme used in legacy ATA controllers & system BIOSes that mapped directly to physical drive characteristics as the names imply. Early versions also required user input for WPC (write re-compensation) and LZ (landing zone) - yuck!
• DMA - Direct Memory Access. A mode of transfering data directly to/from memory without using the CPU. Most SCSI flavors and ATA versions 4 & greater support DMA over the EISA, VLB, or PCI buses. Recent ATA protocols are commonly known as UDMA (q.v.).
• IDE - Integrated Drive Electronics. (Also EIDE, Enhanced IDE.) A common synonym for the ATA peripheral interface (q.v.).
• LBA - Logical Block Addressing. The scheme used by modern controllers & BIOSes to translate a drive's physical geometry (CHS under the legacy system) into a "flat" address space of sequential sectors. 32-bit LBA limits all controllers prior to UDMA-6 (aka ATA-133) to addressing the first ~130GB of a drive at most; the recent standard, while only de facto at the moment, uses 48 bits to effectively circumvent the capacity barrier, at least until we hit the exabyte era.
• Locality - A term to denote the way "random" accesses are often concentrated in certain areas of a storage device.
• MFT - Master File Table. I won't go into the nitty-gritty of NTFS here, but think of it as a FAT (file allocation table) on steroids. For details, see [http://www.sysinternals.com∞ SysInternals] or Helen Custer's classic (if now a bit dated for NTFS 5.0) book∞. Win2k Magazine∞ also has a decent introductory article.
• MTBF - Mean Time Between Failures. An industry-standard specification for drive longevity, usually given in hours of use. The reliability characteristics of electronic equipment can't really be expressed with a single number, but this is the best indicator for what a manufacturer expects their products to be capable of. (Warranties, for example, are driven in one direction by cost consciousness and the other by marketing concerns, such that actual engineering has comparatively little say.)
• PIO - Programmed Input/Output. A method of transferring data over an ATA bus. Various modes supported progressively higher clockrates, topping out at 16.7MB/s. Only used as a fallback mode now; if you don't have DMA checked on all your ATA parts in Device Manager, you're so 90's.
• Random access - Reading/writing data while skipping around on a medium; more easily accomplished on magnetic & optical media than on tape, but still carrying a big performance penalty. The source of your rewinding fees at Blockbuster.
• Rotational latency - The amount of time needed for a drive's platters to rotate into the correct position. Inversely proportional to spindle speed.
• SCSI - Small Computer System Interface, pronounced "scuzzy." An alternative interface standard best known for integrating controller functions into drives, supporting both internal & external devices, really long and oddly expensive cables, [http://www.google.com/search?sourceid=navclient&q=scsi∞ and so on]....
• Sector - The smallest portion of a disk addressable by an OS / driver. Typically 512 bytes.
• Seek time - The amount of time needed for the drive actuators to position the appropriate heads over the requested track.
• Sequential access - The manipulation of data in a linear pattern, i.e. one block after another; the opposite of random access.
• Short-stroke - A pattern of drive accesses that allows the drive's actuator to only move over a shorter portion of its total excursion, improving seek performance.
• Spindle speed - The rotational speed attained by a drive, measured in RPM.
• STR - Sustained Transfer Rate. The amount of data continuously read/written by a drive over a given fraction of time. High STR's can only be attained during sequential access.
• Tagged Command Queueing - The part of a bus architecture that assigns a unique tag to each incoming device command that is released when the command is finished executing. Effectively allows for the host to issue multiple commands to the same device and let the device execute them in any order. Added to the ATA spec in revision 4.
• UDMA - Ultra Direct Memory Access, a method of DMA-based signalling over the ATA bus. Initially a synonym for the ATA/ATAPI-4 specification that defined it; also known as Ultra-ATA. UDMA mode 2 was the first common implementation, providing 33.3MB/s over the same bus width and frequency as PIO mode 4. (I.e., it was "double-pumped" long before DDR RAM and the EV6 bus popularized the notion.) Modes 5 and 6 are in common use providing 100MB/s and 133MB/s operation, being respectively defined in the ATA/ATAPI-6 and -7 (unratified) specs.