What are all the three parameters of cv2.findContours() and it's output?

1 - cv2.findContours(thresh, 1, 2) 2 - image, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_NONE) Can someone please tell me what the 2 parameters in this function mean?? Why we used 1 and 2 in the First example and why we wrote that much for the second one? Thanks in Advance :) P.S. I am a beginner