I'm not sure the exact details of all of it, but i'll say as much as i do know.
Image formats can be interlaced and non-interlaced. interlacing is a method of data transfer that splits pixels into odd and even fields, for a variety of reasons. This is mainly used for video, but i've heard of it for images too. Again, i'm not an expert so you probably want to read the wikipedia entry on it.
http://en.wikipedia.org/wiki/Interlaced_video
Theres 2 ways to improve the quality of an image, and each gives varying results.
One is through more RESOLUTION, or a larger pixel density. This is called PPI (pixels per inch) and sometimes DPI (dots per inch) in reference to printing. There are a few standards roughly followed, 72 ppi is used most everywhere, most of the photos you find on the web will be 72 ppi. 300 ppi is standard for graphic arts work, and you most likely wont be needing much more resolution unless you're working with super large banners or layouts that span across the sides of buildings.
The other is through a LARGER SIZE. I've actually had experience designing for the iPhone mobile platform and i was surprised when instead of upping the resolution, they simply made the image size bigger, maintaining the same aspect ratio. Aspect ratio is the proportions of the image, length and width.
So heres what i mean by theres 2 ways to go about higher quality images. Say you had an image that was 5" x 8" at 72 ppi. thats a total of 2880 pixels, i believe.
That same image could be resized to 10" x 16" at 72 ppi, OR kept at 10" x 16" at 144 ppi.
heres the wikipedia page on resolution:
http://en.wikipedia.org/wiki/Image_resolution
I dont know much about color depth, but i know its expressed in BPP, or "bits per pixel". As a digital artist, i have to be knowledgeable about 2 general types of color profiles, RGB, and CMYK. RGB stands for Red, Green, Blue, and are the primary colors on the additive color wheel. Genrally, any images are usually in some form of RGB because thats what displays, etc use. CMYK (Cyan, Magenta, Yellow, and Key--or blacK) is used for print, and it features the secondary colors on the additive color wheel.
Color is sometimes expressed in hexadecimal code, and this is used widely on the web because its such a standardized way of viewing most colors you could even imagine, but certain colors are not expressed by this. That means certain image formats will allow for MORE data going into each pixel depending on the color that pixel is expressing. This is why one image the same exact size and resolution of another, will be a completely different size.
Again, heres that wikipedia page: http://en.wikipedia.org/wiki/Color_depth
Image compression is the final thing to know about images. Certain formats allow for different purposes, different "color profiles", interlacing, transparency, etc. JPEG is the most common image compressing format and its all over. GIF allows for a little animation, but also transparency, which jpeg does not. Lossy means the image is compressed in such a way, that quality is actually "lost" or affected by the compression. Lossless, as its name says, is without a loss in quality.
http://en.wikipedia.org/wiki/Image_compression
Hope that helps! Good luck with whatever it is you're doing.