These settings control the sampling quality of the rendered images.
Increasing the sampling rates reduces the amount of noise in the images, but at the expense of increased rendering time.
The total number of samples being used can be seen in the information at the top. The actual number of samples is the square of the input number, so in the case of AA samples 3
2 = 9. This is the same for GI samples, which would be 22 = 4. As AA samples is a multiplier for GI Samples, the actual number is 9 * 4 = 36.
Sampling is divided into the following sections: