Invisible zippers have the teeth hidden behind a tape, so that the zipper is invisible. It is also called the concealed zipper. The tape’s color matches the garments, as does the sliders and pullers. This kind of zipper is common in skirts and dresses. Invisible zippers are usually coil zippers.

Only in a blouse, the concealed zipper is stitched upside down and on the left hand side of the side seam. 

You need to press open the curl of the teeth before you sew it on to the garment. While pressing adjust the heat in the iron box as high temperatures can spoil the plastic teeth of a zip. To install an invisible zipper you need to change to ‘zipper foot’.