RotateLeft[expr, n] cycles the elements in expr n positions to the left.
RotateLeft[expr] cycles one position to the left.
RotateLeft[expr, , , ... ] cycles elements at successive levels positions to the left.
Example: RotateLeft[a, b, c, 1].
RotateLeft[expr, -n] rotates n positions to the right. See The Mathematica Book on the web: Section 1.8.9 and Section 1.8.14. See also: RotateRight, Reverse.
RotateLeft[expr, n] cycles the elements in expr n positions to the left. 
, 
, ... 
] cycles elements at successive levels 
positions to the left. 
a, b, c
, 1]
. 