What is shift operator?

The shift operations allow bits to be moved to the left or right in a word. There are three types of shift operations: logical, rotate and arithmetic.

http://www.cs.uaf.edu/~cs301/notes/Chapter5/node3.html

$a & $b    -  And        -  Bits that are set in both $a and $b are set.
$a | $b    -  Or (inclusive or)    -  Bits that are set in either $a or $b are set.
$a ^ $b    -  Xor (exclusive or)-  Bits that are set in $a or $b but not both are set.
~ $a    -  Not        -  Bits that are set in $a are not set, and vice versa.
$a << $b    -  Shift left    -  Shift the bits of $a $b steps to the left (each step means "multiply by two")
$a >> $b    -  Shift right    -  Shift the bits of $a $b steps to the right (each step means "divide by two")