What does this line of code mean?

Hello,

I want to know how object detection using SURF works and I found this code:

Object Detection in a Cluttered Scene Using Point Feature Matching

In the above code, I don't understand what the following lines mean? Can somebody please explain it to me? It say's "Display putatively matched features.", but I don't get it how.

matchedBoxPoints = boxPoints(boxPairs(:, 1), :);
matchedScenePoints = scenePoints(boxPairs(:, 2), :);

I believe that the variable "boxPoints" is a key feature and "boxPairs" is the matched feature using their descriptors, right?

Also, it would be great if somebody could explain me how the affine transformation in the code works and is there any equivalent python code?

Thank you very much.