To add to the excellent comments above -- what you use depends on how you want to "reference" these groups of actions.
A sub-routine is a "mini macro" you can use in other macros. The big benefit of using them is that you can make a change in the sub-routine and all the macros that use it immediately benefit from the change -- you don't have to make the same edit in 100 different places. The downside is that while you can "individualise" a sub-routine so that it behaves differently in different macros that can soon get pretty complicated.
You can also put a bunch of actions into a Group action then Favourite that Group. This is a "template" system, making it easy to add those actions to a macro in the Editor, and that macro's Group is independent of all others -- you can make changes in one without effecting others.
A good example of a sub-routine would be a checkout or invoice calculation -- pass in item costs and number purchased. Your sub-routine would then handle the dialogs for tax rate and shipping options and return a total price. You could use that in many macros, and when tax rates change you only have to make one update.
An example of a Favourited Group could be an "incrementing loop" routine where you are always going to want a variable, a loop, a test, an incrementer -- but what happens in the loop will vary macro to macro.