Understanding Bitmap Images

The term 'bitmap' can mean a few different things.

Some people use it to refer to any pixel-based image.
Some people use it to refer to clickable 'image maps.'
It's also the name of the native Windows file format.
Right now, we're considering it as a color mode.

The bitmap mode is the simplest of all color modes.
It has a bit-depth of one.
It allows one bit of data to each pixel.

A bit is the smallest possible unit of digital data,
the atom of the digital world.

Thus the value of each pixel might be expressed, in binary,
as either 0 or 1.

Each value corresponds to a color.

0 is black.
1 is white.

And that's all there is to it.

Obviously, this is somewhat limiting.