A logical shift is often used when its operand is being treated as a sequence of bits rather than as a number.
If the bit sequence 0110 1111 1010 0011 were subjected to a logical shift of four bit positions to the left, the resulting bit sequence would be 1111 1010 0011 0000
Note that the farthest-left quartet of bits, 0110, was lost in the operation, and the rightmost 4 bit positions were filled in with zeros.
For a simpler explanation, the bit sequence 0111 1001 which is subjected to a logical shift of two bit position would yield the bit sequence 1110 0100.
(This entry is from Wikipedia)