Azulejo, or glazed, usually blue, ceramic tile, became a typical feature in Portuguese culture. These tiles are found on many types of surfaces including the interior and exterior of churches, palaces, railway stations or even ordinary houses. It is a major distinguishing factor of Portuguese architecture used not only as ornamental art form but also had functional use like temperature control in some homes.
These azulejos became an important feature in the Portuguese baroque period. The tiles were produced using the majolica technique. The ceramic piece is covered with and opaque white glaze, painted with color pigment, then fired or glazed.
video demonstrating majolica technique: http://www.youtube.com/watch?v=YHK_y_Sbsbg