Bit: The smallest unit of memory; a contraction from ´binary´ and ´digit´. Binary digits are 0 and 1, also known as ons and offs.

Bit Depth: This refers to the color or gray scale of an individual pixel. A pixel with 8 bits per color gives a 24 bit image. (8 Bits X 3 colors is 24 bits.) CCD are colored in a pixel by pixel method.

30/32 bit color is billions of colors. (Only supported with high-end CPU´s.)
24 bit color resolution is 16.7 million colors.
16 bit color is 32,000 colors. ( this is the Macintosh Standard )
8 bit color is 256 color. ( this is the Windows Standard )
8 bit gray scale is 256 shades of gray
4 bit 64 colors or gray
2 bit black or white.

Bitmap: The method of storing information that maps an image pixel, bit by bit. There are many bitmapped file formats, .bmp, .pcx, .pict, .pict-2, tiff, .tif, .gif (89a), and so on. Most image files are bit mapped. This type of file gives you the ´jaggies´, when examined closely you can see the line of pixels that create edges. Bitmap images are used by all computers. The desktop or screen information for all Windows machines uses .bmp files, while the Macintosh uses pict files.

BULB Photography: This term refers to a standard setting for slow shutter control. This is a special setting for low light situations, similar to the Shutter Priority Mode. Timing for the shutter is set in the Menu options. The shutter remains open for a longer period of time and the Flash is disabled to capture more of the natural light. Although this is effective, it is not as sophisticated or precise as Shutter Priority. 

Byte: A group of 8 bits; the basic unit of information