Exposure triangle is all about the three things ISO,SHUTTER SPEED AND APERTURE.
ISO
Iso stands for International Standards Organization.In photograph ISO is used for the ISO affecting the sensor. To be more specific, the ISO determines how well exposed a photo will be by changing the sensitivity.
Sutter speed is for exampel the slower the shutter speed, the longer the exposure time.
Aperture is the unit of measurement that defines the size of the opening in the lens that can be adjusted to control the amount of light reaching the film or digital sensor.