(AC-3) This is the core technology for Dolby, very commonplace, available on all DVD's and HDTV broadasts, offering up to 5 speakers. Encoded at 24-bit/48kHz with a transfer rate of 640Kbs.
(Digital Theater System) This is DTS's core technology, not as common as Dolby Digital and has 5 speakers, too. It is also encoded at 24-bit/48kHz but has a higher transfer rate (1.5Mbs) than Dolby Digital and uses less compression:
(Dolby Digital 5.1EX) This was Lucasfilm's way to make more money and plug "Episode One" back in 1999. Turning 5 speakers into 7 speakers with the addition of 2 NON-DISCRETE "center rear" speakers (in MONO), working closely with THX, Dolby Labs had to call this new audio format "THX Surround Ex" for at least 3 years until the contract was up and it was renamed "Dolby Digital Ex":
(DTS-"Extended Surround") DTS's revenge for "Dolby Ex", the "DTS-ES 5.1 Matrixed" is also 7 speakers instead of 5 and the 2 added NON-DISCRETE "center rear" speakers (also in MONO) can be discrete but usually aren't and when they are, it is then called "DTS-ES 6.1 Discrete", thus an improvement over Dolby Ex and continuing the arms race between the two digital surround formats:
(ProLogicIIx) In an attemp to upstage DTS's "Neo-6" technology (which came first) and make 2-speaker (stereo) recordings sound like 7-speaker (surround) recordings, to of course play through all of those speakers people allow in their living rooms, Dolby invented this, (a bit late in the game) and it works okay (like "Dolby Ex" the 2 "center rear" speakers were still in MONO):
(DTS NEO-6) As I said before, DTS wanted to make stereo play out of ALL 7 speakers way before Dolby, and obviously motivated them to do the same, once again fueling the war between the relatively similar audio formats (and like "DTS ES" the 2 "center rear" speakers were also in MONO):
(Dolby Digital Plus) This is the only COMPRESSED audio format new to Blu-ray Disc, encoded at 48 kHz/24-bit and offers a less compressed audio signal than "Dolby Digital" and is similar to regular "DTS" (1.5Mbps). It's small enough to fit inside future Hi-Def broadcasts and is currently available in 5 speakers:
(LPCM) All Blu-ray Disc players can decode this format which is capable of encoding at 24-bit/192kHz and having up to 7 speakers. Of the 3 completely uncompressed HD audio formats the "Uncompressed PCM" is the lowest quality, but still far surpasses regular "Dolby Digital" and "DTS" (and "Dolby Digital Plus"):
(TrueHD) This is the other of Dolby's formats for Blu-ray Disc, also available in up to 7 speakers. It can be encoded at up to 24-bit/192kHz and is the second of 3 uncompressed HD audio formats, sounding better than "Uncompressed PCM".
(Master Audio) This is the BEST of the 3 uncompressed HD audio Blu-ray Disc formats (sounding better than "DolbyTrueHD") and capable of being encoded at up to 24-bit/192kHz and 7 speakers. This is the top-of-the-line for Blu-ray Disc surround sound (or ANY surround sound, so far).
NOTE: Currently all 3 uncompressed HD audio formats are mostly available at 24-bit/48kHz (or less). Blu-ray Discs can be recored at up to 24-bit/96kHz (for 7 speakers) and 24-bit/192kHz (for 5 speakers).