Strange operators

[Yen]

Explain these to me! Please.

NPC Code:

---

Bitwise-Or                a | b

Bitwise-And               a & b

Bitwise-Shift left        a << b

Bitwise-Shift right       a >> b

Bitwise-Invert            ~a

Bitwise-Xor               a xor b (operator ^ already used for power)

Bitwise-Or Assignment     a |= b

Bitwise-And Assignment    a &= b

Shift Left Assignment     a <<= b

Shift Right Assignment    a >>= b

---

Also, why do people use := sometimes, instead of =?