Single malt dominates the market but blends are also popular and made from a mixture of malted grains, always with some percentage of barley. Irish on the other hand, is mostly triple distilled, which makes it renowned for its smoothness. It is also more likely to be made up of a combination of grains, not just barley.
Triple-distillation creates whiskies that are often described as smooth. By refining the spirit over three distillations rather than two, the distiller concentrates a particular fraction of aromatic and flavorful compounds, which results in a smoother taste and a subdued finish.