This command will move (also known as shift) the bits in a number to the left or right.
If you pass in a positive shift, the bits in value will be shifted to the left, making the number bigger. If you pass in a negative shift the bits will be shifted to the right making it smaller.
Each bit shifted will either increase or decrease the value by a power of two. Eg a shift of 1 to the left will double the value, and a shift to 2 to the right will quarter it.
See also the Bit Set, Bit Test, Bit And, Bit Or and Bit Xor commands.