Shortbread is a simple sweet biscuit made of sugar, butter, and flour. The high proportion of sugar and butter to flour makes the cake "short", or crumbly (as opposed to long, chewy bread).
Shortbread was historically associated with Scotland, where the first recipes were recorded. The oldest printed recipe for shortbread is from 1736, though historical references to it from the 12th century can be found. In the United Kingdom, it is often convention to refer to "Scottish Shortbread," even though it is eaten across the country.