Span

i;;j represents a span of elements i through j.

i;; represents a span from i to the end.

;;j represents a span from the beginning to j.

;; represents a span that includes all elements.

i;;j;;k represents a span from i through j in steps of k.

i;;;;k represents a span from i to the end in steps of k.

;;j;;k represents a span from the beginning to j in steps of k.

;;;;k represents a span from the beginning to the end in steps of k. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.