ISO of camera or mobile indicates light sensitivity of the image sensor. Higher ISO enable a camera to take images in dark environment.
Now it is true that if you take a photo with higher ISO then your image quality may be reduced as it may appear noisy. However one can get less noisy picture even in higher ISO if the aperture is large enough.
Shutter speed indicates how much time the shutter will remain open. If you want to capture a fast moving object then you have to select fast shutter speed. If you want to take a photo in dark environment the you can select shutter speed slow as slow shutter speed will able to collect more light. But one should know that if you select slow shutter speed then you have to hold the camera or mobile steadily as it may cause shaky/blurry images.
Aperture is basically a window through which light comes inside the camera. Large aperture significantly improve low light photography. It controls depth of field in a photo. Aperture is a factor for background blur or bokeh effect.
Control the amount of light coming to the sensor
Control Depth of field
f- stop or the f- number is nothing but a numbering system to indicate how much the aperture is open.
For example f/1.4, f/1.7, f/1.8, f/3.5, f/5.6, f/8, f/16, and so on. Here f/1.4 indicates that the aperture is wide open.