This is a type of leavened bread in which baking soda is used as the raising agent instead of yeast.
The main ingredients are flour, baking soda and buttermilk, and it is a reaction between the buttermilk and the baking soda that causes carbon dioxide to be produced, causing the bread to rise.
A version called farl is popular in Northern Ireland. The bread is cooked on a griddle to form a 2cm thick disc, and then cut into quarters. (The term farl can also refer to similarly shaped potato cakes.)