Pretend that (for some reason) you want to send this image to SmileBASIC:
If you try to convert it directly to a format that works in SB, it ends up looking like this:
That's because SB only uses 16 bits to store colors instead of 32.
However, you can use dithering to make it look better:
This type of dithering works by calculating the difference between the 32 bit color and the 16 bit color, and spreading the error to surrounding pixels.
For example, if one pixel is made slightly darker when converting to 16 bit, the surrounding pixels (the ones that have not been converted yet) will be made slightly lighter.