Iris is software for eye protection, health and productivity.
The 2 most popular things of Iris which probably brought you here are:
You can decrease the amount of blue light emitted from the screen
Control the brightness without PWM flicker.
There are several different modes and several different types of Iris. This are basically some preset values that many people use. Aside from this you can customize Iris a lot. I know that it can be a little hard for non-technical people, but I'm doing my best to make it as easy to use as possible.
By default Iris works automatically and detects if it's day or night. Based on that it will change your screen Color Temperature and Brightness. When you open the control panel of the program you can select different modes and types of Iris.
If this is still so hard for you try Iris mini which is smaller version of Iris with smaller size and lower CPU usage. Both Iris mini and Iris are free, but there are some Pro versions with more features, because I work on Iris full time and want to make sustainable business from it for me. This is my passion and my dream.