Ken,
Imagine a piece of graph paper. You can ‘draw’ a line by filling in adjacent squares, or you can get out a ruler and just draw from point ‘A’ to point ‘B’.
The first method is an analogue for a raster image and the second for a vector image.
The raster image is just a collection of pixels (like the squares on the graph paper) and there is no real relationship between one pixel and any other pixel.
On the other hand, a vector is a series of mathematical expressions such as "draw a line from point x,y to point x1,y1". In this case, every position upon that line is dependent upon the whole line.
The difference between BMP and Rastor images?<<
A .bmp is just one particular file format of many in which a raster image can be saved.
Some formats can save both raster and vector format within themselves. Examples are .pdf, .psd and .eps, although there are other formats that can do this also.