a += b Roughly equivalent to a = a + b
a -= b Roughly equivalent to a = a - b
a *= b Roughly equivalent to a = a * b
a /= b Roughly equivalent to a = a / b
a //= b Roughly equivalent to a = a // b
a %= b Roughly equivalent to a = a % b
a **= b Roughly equivalent to a = a ** b
a &= b Roughly equivalent to a = a & b
a |= b Roughly equivalent to a = a | b
a ^= b Roughly equivalent to a = a ^ b
a >>= b Roughly equivalent to a = a >> b
a <<= b Roughly equivalent to a = a << b

a += b Roughly equivalent to a = a + b
a -= b Roughly equivalent to a = a - b
a *= b Roughly equivalent to a = a * b
a /= b Roughly equivalent to a = a / b
a //= b Roughly equivalent to a = a // b
a %= b Roughly equivalent to a = a % b
a **= b Roughly equivalent to a = a ** b
a &= b Roughly equivalent to a = a & b
a |= b Roughly equivalent to a = a | b
a ^= b Roughly equivalent to a = a ^ b
a >>= b Roughly equivalent to a = a >> b
a <<= b Roughly equivalent to a = a << b

What do you mean "Roughly equivalent"? a += b is the exact same thing as a = a + b .

Just like in C, a += b does the same thing as a = a + b, but the code produced is more efficient. So, I think, the roughly is there for the sticklers in life.