Ok, so to make a very short 101 explanation:
- ISO: is the sensibility of the film (or sensor). Higher ISO means more sensible so less light needed.
- shutter speed: is the time the film or sensor is exposed to the light. Higher shutter speed means less blur on the image but also a darker image (the light has less time to expose the film or sensor).
- aperture or f-stop or f-number: is how open the diaphragm is. Higher f-number means a diaphragm less open so less light but more depth of field.
All of those are independent settings.
NB: with digital camera you only have one sensor so you also have only one ISO sensibility (you can't change the film for another one who is less or more sensible as the film is the sensor...) but you can add gain (amplify) after the image is taken, however it doesn't make the sensor more sensible, it's like the brightness setting in photoshop for example, you amplify the useful signal but you also amplify the noise (example of a noisy image:
https://en.wikipedia.org/wiki/Image_noise#/media/File:Highimgnoise.jpg) so you can't add 24 dB of gain and expect a good image quality (but if you're already maxed out on the light, the shutter speed and aperture settings you have no other choice...).
NB²: a rule that can be useful
https://en.wikipedia.org/wiki/Sunny_16_ruleI bet there's a lot of tutorials on the web on how to use a camera in manual mode for beginners so you can read those while waiting for the crash course chapter in the Chronos' manual.