Bitmap image files, otherwise seen as BMP or DIB, are Raster graphics used to store bitmap digital images.
In older versions of Microsoft Paint, BMP files were the default save format.
BMP are powerful and can be stored at any resolution, in full color, lossless and with alpha channels. File sizes are rather large.
Along with PNG images, BMP are still used for printing due to their high quality and lossless nature, unlike JPEG and GIF which use compression.