ISO

How sensitive the sensor is to light 

iso 6400

iso 25600

iso 100

iso 100

                             Aperture     

                        The size of the diaphragm at a given moment.
The bigger the diaphragm the less thing in focus but the more light let in, the smaller the diaphragm the less light let in but the more things in focus                

f1.2

f1.2

f4.5

f6.3