resolution x 24 32

[matriplex]

I have some videos and I use some program to have information about them like gspot, mediainfo etc.

some of them say for video 320x240x24 352x288x24 ....
for example for the first video I know that 320 is: width 240 is: height 24 is?

is it color depth? what is it for?
what are the advantages and disadvantages to be big(32) to be small(24)?
for example I have an 320x240x32 I converted it 320x240x24 do I lose quality?
for example I have an 320x240x24 I converted it 320x240x32 do I increase quality?

[mats.hogberg]

Yes, it's color depth (in bits/pixel).

for example I have an 320x240x32 I converted it 320x240x24 do I lose quality?

Yes

for example I have an 320x240x24 I converted it 320x240x32 do I increase quality?

No

/Mats

[jagabo]

for example I have an 320x240x32 I converted it 320x240x24 do I lose quality?

No. 32 bit color is usually 8 bits of red, green, and blue (ie 24 bits of color), and 8 bits of alpha channel or unused.

for example I have an 320x240x24 I converted it 320x240x32 do I increase quality?

You will still have 8 bits of RGB, all you've done is added 8 unused bits.

The next step up from 24 bit color, in terms of additional bits for the RGB primaries, is usually 48 bit color with 16 bits for each primary.

[matriplex]

which one is true? mats.hogberg' opinion or jagabo's?
please help me.

[mats.hogberg]

Well, since every conversion like this requires a reencode, and every reencoding reduces quality (unless you encode to a lossless format, and get the same q as the source - the absolute best you can ever hope for), you will lose quality whatever way you go.
As for the technicalities, I'd say jagabo is correct - the extra 8 bits/pixel is usually alpha channel.

/Mats