What are augmented assignment operators? How are they useful?

What will the result given by the following?

(a) type (6 + 3)

(b) type (6 -3)

(c) type (6 *3)

(d) type (6 / 3)

(e) type (6 // 3)

(f) type (6 % 3)

Given str1 = "Hello", what will be the values of:

(a) str1[0]

(b) str1[1]

(c) str1[-5]

(d) str1[-4]

(e) str1[5]

Two objects (say a and b) when compared using == ,return True. But Python gives False when compared using is operator. Why? (i.e., a == b is True but why is a is b False?)