Excel calls it "Grouping"
With Sheet1 active hold down the Shift-key and click on sheet3
this will Group contiguously -- To Ungroup right-click on any one an
select Upgroup Sheets..
For Non-Contiguous hold down the Control key as you select...
HTH
Don't forget to "UNGROUP"!!! Failing to do so when you should can really
screw things up for you...