Irish baking over the centuries has been affected by two main factors. The first is our climate. The influence of the Gulf Stream prevents either great heat in the summer or cold in the winter. As a result, hard wheats, which need such heat and cold, don't prosper. Those wheats make flour with a high gluten content that responds well to being raised with yeast. But soft wheats do grow well here.
The other factor has been the abundance of fuel. Ireland's various medieval overlords could never exercise the tight control over forest land that landowners did in more populous, less wild areas, like England and mainland Europe. This meant that Irish people had less trouble getting their hands on firewood. Where there was no wood, there was almost always heather, and usually turf too. As a result, anyone with a hearthstone could bake at home whenever they wanted to, rather than needing to use a communal bake-oven to conserve fuel.
These two factors encouraged the Irish householder of the past two centuries to bypass yeast for everyday baking. The primary leavening agent became what's now known here as bread soda -- just plain bicarbonate of soda, to US and North American users. Hence the name soda bread. But for a long time, most bread in Ireland was soda bread: "bakery bread" was only available in big cities. Soda bread was made either in a pot or casserole over the fire, or else baked on a bakestone, an iron plate usually rested directly in/on the embers. From these two methods are descended the two main kinds of soda bread eaten in Ireland, both north and south, to the present day.
In Ireland, "plain" soda bread is as likely to be eaten as an accompaniment to a main meal (to soak up the gravy) as it's likely to appear at breakfast. It comes in two main colors, brown and white, and two main types: cake and farl. People in the south of Ireland tend to make cake: people in Northern Ireland seem to like farl better -- though both kinds appear in both North and South, sometimes under wildly differing names.
Cake is soda bread kneaded and shaped into a flattish round, then deeply cut with a cross on the top (to let the bread stretch and expand as it rises in the oven). This style of soda bread is normally baked in an oven.
These days we'd normally bake it on a baking sheet / cookie sheet. But in earlier times, before ovens were commonplace, cake was routinely made in deep, lidded iron casseroles, hanging over the open fire or sitting right in it -- the casserole lids being concave to hold coals or burning turves from the fire on top, so that the bread would bake evenly in radiant heat from all sides.
The cake style of soda bread can of course be eaten hot. But it's more usual to let the loaf cool down before eating it (it's a little easier to handle then). It's also a lot easier to slice, and that's the way it's normally seen in supermarkets and convenience stores country-wide, in both brown and white versions.
Farl is rather different. When making farls, the soda bread dough is rolled out into a rough circle and cut all the way through, crosswise, into four pieces or farls ("farl" is a generic term for any triangular piece of baking), and usually baked in a heavy frying pan or on a griddle, on top of the range or stove rather than in the oven. It's a flatter bread than cake, and moister after the baking's finished. Each farl is split in half "the wide way" before eating. It's best when eaten hot off the griddle, but it's also allowed to cool and then grilled or fried as part of other dishes, especially the famous Ulster Fry.
One important note: in the US and North America generally, there's a tendency to think of soda bread as something with fruit in it. This is not the case in Ireland. While people have for many years sometimes added fruit to the basic dough as a treat or for a change of pace, this is not usually referred to as soda bread, but as tea bread, fruit soda, tea cake, and by many other names. We have recipes for these below as well. But everyday soda bread in Ireland does not contain fruit. (source: europeancuisines.com)