What is << operator in cout

Question

below code outputs 2 instead of 11. why ?

cout << (1<<1);

Answer 1

because here 1<<1 act as left shift operator..
1<<1 value is 2 and 2 print by cout..

Answer 2

<< is bitwise left shift operator

The left-shift operator causes the bit pattern in the first operand to be shifted to the left by the number of bits specified by the second operand.

So 1 << 1 = `0000 0010`
evaluates to 2

Answer 3

never come across this operation...any usecase of same will be helpful to make me digest this easily

Answer 4

<< operator is also called as insertion operator