Masa harina is a type of corn flour that is used to make a wide range of Latin American foods including Mexican corn tortillas and tamales. Unlike ordinary corn meal, the kernels used to create masa harina are treated with slacked lime prior to grinding. The resulting corn flour has a fine texture and reconstitutes to make a very smooth dough. It also has more nutritional value than corn meal or flour that has not been treated with the calcium rich lime.
Masa harina is widely available in many parts of the United States in grocery stores but it is also inexpensive and quite accessible online.