In article , Jim-P
wrote:

In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

it's the same with digital cameras, except that higher iso has more
noise.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

it does not.

like film, the sensitivity of a sensor is fixed.

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

yep, and with amplification comes additional noise, just as faster
films were more grainy.