Scientists have discovered that there's another taste with its own taste receptors that we haven't been aware of. It's umami! What causes us to taste umami is little more complicated than some of the other basic tastes. Salt makes food taste salty, and sugar makes food taste sweet. Umami is often created through the ingredients we use and the way we cook them. It's more common in some cuisines than others, and there are ways of increasing it (MSG, anyone?).
To learn about the flavor that is very often ignored but makes food taste better, click through this gallery.