Hi Hughie,
This is my way of explaining.
In those days if you asked as you entered Ballyshannon your ancestors name I am sure you would be told where they lived, or even where they went shopping!
Townland is like a block in the USA. then if there is another name to the townland it's like the name of a place within the block, like a number in the block.
Barony
+ireland baroney - Search (bing.com)
Union ? something like the above. The town and surrounding area.
Parish ......... these often change, it's a Church in the area, some amalgamate but the old names are still used.
Zip code. a USA thing. Only a few years ago ireland had "Postal Code". (these are far better than the UK ones)
Need to Find a Postal Code in Ireland? Start Here.
Province this is another ............On the first map, Ulster has a red line, the counties that are in the top part belong to the UK.
There three counties in Ulster that are in the Republic of Ireland.
ireland province - Search (bing.com)
Then in the Census you have DED
District Electoral Divisions.
In Church records you have a Diocese.
Some of these cover three counties.
All good fun searching.
Margot