Could I get a definition of AC3 2CH, AC3 5.1CH and DTS formats that I have seen used in videos?

Dolby Digital 5.1 (AC-3)
Surround sound technology that delivers high-quality digital audio for up to 5.1 discrete channels (Left/Center/Right/Left surround/Right surround/Low-Frequency Effects). The 5 speaker channels produce a directional & more realistic effect & the Low- Frequency Effects (LFE) channel (usually reproduced through a subwoofer) can often be felt as well as heard. Found in: DVDs; DVD players; broadcast programming in HDTV, digital cable, and (DBS, DTH) direct broadcast satellite (DirecTV/Dish/Sky TV); PCs; Microsoft Xbox game consoles; digital TVs; automotive DVD-Audio/Video players; automotive video, networking & home audio/video receivers; film soundtracks encoded in Dolby Digital.

Dolby Digital 2.0
Basically the same as above expect theres only 2 channels (Front left/right).

DTS
Is similar to Dolby Digital 5.1 except they use a different method for encoding the audio. Supposedly it's a more lossly format than Dolby Digital, but it's encoded at higher bit-rates & seems to be the choice amongst most DVD audiophiles for best quality sound.

You can find more out on both at;
http://www.dolbylabs.com
http://www.dtsonline.com

Channels

Thanks. Was wondering if all these channels were needed for a DVD player hooked to TV.

Right. No, (most) DVD players will automatically down-mix the audio to stereo if that's all you're using (Which you are if you're TVs doing the audio output).

Audio

If my TV supplies the audio I do not need ac3 5.1 and DTS channels. Right.

You're needlessly asking questions. Just plug your DVD player into the TV and watch your movies.

Question

Not when ur using Shrink and you need to trim.

that wasnt the question he was asking mr. smart mouth. Besides, 1st audio track on a dvd is usually 5.1 sound. Why would you even rip that track out? If he just had a stereo tv, the 5.1 track would be outputted into stereo.