What does += mean?

Question

I've done some challenges in which i encountered a += b, but I don't know what it means. so I wondered if someone could tell me what it means.

Answer 1

a += b is equivalent to a = a + b

a -= b is equivalent to a = a - b

a /= b is equivalent to a = a / b

a *= b is equivalent to a = a * b

Answer 2

thank you so much Ismail Bina!