; ; ... evaluates the in turn, giving the last one as the result.
CompoundExpression evaluates its arguments in a sequence corresponding to the control flow.
The returned value can be the result of Return[expr].
The evaluation of the can be affected by Return, Throw and Goto.
; ; returns value Null. If it is given as input, the resulting output will not be printed. Out[n] will nevertheless be assigned to be the value of .
See The Mathematica Book: Section 1.2.6 and Section A.2.7.
See also: Block.