1040ST (Refered to on ST case):
See above, this means 1024k. Further specs, though never official Atari labels can include the 2080 and the 4160 for 2 megs and 4megs respectfully.

Blitter:
ST Graphics chip fitted in standard STE's, higher spec STFM's and Mega ST's and STE's.

Cartridge Port:
As far as I know this is pretty unique for a 16bit computer. It had 128k of possible storage ( i.e a lot less than a floppy disk) and therefore apart from a couple of attempts was not used for programs. It became useful mainly as a security dongle port for music programs. It also unfortuantly mean't that if you use your super Hades '060 or Milan for music, you have to buy a cartridge port extension...

DSP:
Falcon's "super" chip which allows its music abilities to outshine most comparable competition. Also fully usable for other Data processing tasks.

GEM:
Graphical Environment Manager
Very similar to the Apple Macs operating system (so similar Apple in fact sued the developers Digital Research) GEM allows the graphical manipulation of files.

GDOS:
Graphics Device operating system.
Extension for TOS/GEM allowing printing. The original was pretty dodgy really, and there have been several attempts to improve it. Originally GDOS was meant to be built into the ROM but delays meant that it never got there. This severly handicapped the ST and it was not until the arrival of NVDI and SpeedoGDOS that the ST got a font system worth talking about.

Mega 1 ST:
Mega ST with 1 meg of memory. The Mega ST is a standard ST with blitter re-packaged in a smaller desktop case and has a second keyboard.

Mega 2 ST:
As above with 2 meg

Midi Sockets
The original ST was a triumph amongst musicians thanks to these ports being built in to the standard design. It allows any ST with a sequencer to interface, completely with a keyboard, and make beautiful music together! (ooo errr!) The design was carried over into all the Atari computers and the ability can be extended to the clones as well.

ST Resolutions
The Atari ST (in whatever form) was capable of three resolutions without added graphics cards: ST Low; 320 x 200 in 16 colours ( from a pallette of 512 on STFM's ( and older) and 4096 on the STe): ST Medium; 640 x 200 in 4 colours ( from a pallette of 512 on STFM's ( and older) and 4096 on the STe): ST High 640 x 400 in 2 colours ( black and white). Low and Medium were used a lot by casual and average users, as they could be used on a standard TV set ( also on a colour monitor). ST high was more for the serious user ( at the time/ though now it is the ST standard) and required a special mono monitor.

TOS
The Operating System/ Tramiel Operating System
Many different versions of the Atari version of DOS. TOS 1.00 originally came on disk but was soon moved into ROM (Read Only Memory). This resulted in a "indestructible" operating system that would always be available in the case of an accident. It also however resulted in a TOS that was difficult to patch when bugs became apparent. TOS 1.02 fixed some of the bugs in TOS 1.00 and included support for the Blitter Chip. It was still awful with hard disks however. TOS 1.4 Improved hard drive support and fixed a lot of the bugs of the previous versions. TOS 1.6 is essentially a version of TOS designed specifically for the STe. TOS 2.6 is the final version of TOS available for the standard ST and includes a lot of improvements. TOS 3.5/3.6 are basically TOS for the TT computer. TOS 4.02 and TOS 4.04 are the Falcon versions of TOS. Atari never released a TOS version above 4.04. Various developers have fiddled with TOS however. The Milan contains TOS 4.5, which essentially 4.04 fixed to run on the Milan. The Hades had a patched version of TOS 3.6. Alternatively the MAGIC and MiNT operating systems completely replace all or bits of TOS.

Yahama Sound Chip
The source of many of the original STFM's few faults. Three tone sound generator, capable of producing the most awful sounds known to man if used by a tone deaf or lazy musician/ programmer ( Read most of them in the late 80's early 90's). Also had control over some other ports (frighteningly).