What exactly is a townland? A townland is the smallest surveyed unit of ground in Ireland. It is basically the address of most people in rural Ireland. It is not a village, although there may be one within a townland. I like to think of them as a cow or sheep pasture with boundaries. They may or may not have houses.
Townland names will be seen in church registers, deeds transactions, birth, marriage, death certificates, directories and in newspaper accounts. While the concept of a townland goes back into antiquity, the boundaries, and often their names do not. It was the Ordnance Survey teams who by the early 1830s had set boundaries, names and switched Ireland from Irish Acres to English Acres (1 Irish Acre = 1.6 English Acres).
A quirk you will encounter is that what the Ordnance Survey teams designated as a townland, may not be what the local people used in the records. This is found commonly in Roman Catholic records, and even civil registration, although the government records were supposed to use the standardized names.
The typical townland ranges from a few hundred acres to maybe a couple of thousand.
Either way, they are small by American and Canadian standards! They are not square, but follow roads and geographic features. A typical road map may list townland names, but not townland boundaries. The more detailed maps will show townland boundaries, especially the 6 inches to the mile maps drafted in the 1840s. One important site with maps is www.askaboutireland.ie