Some people in here came very close, but still inaccurate. Leave it to the sound card buff.
The Original Soundblaster has an 11-voice yamaha 2-operator FM chip and an 8-bit digital DAC capable of 22khz mono recording/playback. Also included the 12 stereo squarewave voices of the original (failed) GAMEblaster card.
SBpro 1.0 has a 22-voice 2-operator FM chip and a DAC capable of stereo 8-bit sound @ 22khz or mono 44.1khz. Some also had Gameblaster sound.
SBpro 2.0 replaced the 2-op FM chip with the 4-op OPL3. Dropped the Gameblaster.
SB16 comes out with full 16-bit sound @ 44.1khz mono/stereo. Still has OPL3 FM. Some models begin to emerge with the WAVEblaster header, to snap on a General MIDI daughterboard.
(as an interesting note, this is the first sound card to PROPERLY work as a Roland MPU-401 MIDI controller in all software, including games.)
SB16 comes out with other models, including SCSI-2, multi-CD (with interfaces for Sony, Mitsumi, and Panasonic (its own). Some with IDE as well. There is an optional DSP on some of these boards (I forget the name- it's NOT AWE) that allowed Qsound which was kinda' neat but flopped.
SB32/AWE32. 32 no longer means "bits". It now has a hardware General MIDI synth built on the board, capable of 32-voice polyphony, in addition to SB16 digital sound. The
Advanced
Wave
Effects make the MIDI music sound all the better, and also give the option of SoundFonts- instruments going above and beyond the hard-coded General MIDI patchset. There are still a few games out there that use SoundFonts- the best being Magic Carpet 2 (as far as I know- I hear Final Fantasy PC uses it too.) Soundfonts were stored in RAM on the card. SB32 had 0 RAM, AWE32 had 512k. Most cards (except value) let you add 2 30-pin SIMMS of either 1, 4, or 16MB amounts. I still have my pair of 4MB, although at the time, it was for my Gravis Ultrasound PnP... I moved to the AWE32 for game compatibility.
AWE64. Things get wacky here. They now have a 32-voice hardware synth from the AWE32, and an optional 32-voice software synth that sucked. (That's the synth used in the PCI-series cards.) They also removed the option to add standard 30-pin RAM and used their own proprietary modules that cost a vital organ. Other than that, it's an AWE32. The card of note is the AWE64 Gold, which had the S/PDIF interface and 4MB RAM and Gold connectors! A very nice card I wouldn't mind getting again, especially if someone has a memory module for it! Digital (WAV) sound hasn't changed since the SB16.
Ensoniq PCI, PCI 128, PCI 512, etc. All these puppies are based on the same Ensoniq chip (compatible with the Ensoniq Soundcape/SBpro for DOS, since SB16 compatibility is no longer possible in DOS for this card.) They use a software synthesis that doesn't take up much CPU time, but sounds bad for General MIDI in comparison to the ol' AWE32/64. Most people with these cards are not playing MIDI music anyways.
SB Live! A dandy of a card... has two hardware synthesizers of 32 voices each. Shares the pool of RAM allocated from the system to hold Soundfonts and has improved digital sound (because now you can stream multiple audio channels! Forgot to mention the PCI series cards can do this as well- somewhat.) MIDI music is 95% as good as the AWE32, but with HUGE soundfonts and 2x polyphony. Life is good for amateur musicians.

Accelerated D3D audio. Environmental Audio (EAX) is introduced and later added to some PCI series cards too- adds neato 3D sound and audio "alteration" to make it sound like the game environment. It sounds VERY cool to be in a cave and SOUND like you're in a cave. Easy to implement, and game developers flock to it, leading the the ultimate demise of A3D which was superior for 3D sound.
All other Live! cards are only slight variations of the above.
That's not including any COMPETITORS' sound cards.

The Gravis Ultrasound series were real nice for musicians... still have a couple of 'em myself.
