Shade and transparency are two ways of setting more precisely how a specific color will be applied on your items. Shades and transparencies are fake effects that will be interpreted by some later elements of the printing workflow, such as Raster Image Processors, to know how the set color can be rendered with pure colors. This is the key point of reproducing colors: if you want a gray, you'll generally have a black color for that. In offset printing which is the reference, the size of the point will vary relatively to the darkness of the black you chose. This will be optically interpreted by the reader.
Each color property has a Shade value. The default is set to 100 percent, meaning that the color will be printed fully saturated. Reducing the shade value will produce a lighter color. When at 0 percent, the color, whatever it may be, will be interpreted as white.
On a pure color item like any primary or spot, changing the shade won't affect the color...