Transparency is such an important aspect in games that the Standard Shader supports three different ways of doing it. This recipe is useful if you need to have realistic materials with transparent or semi-transparent properties. Glasses, bottles, windows, and crystals are good candidates for PBR transparent shaders. This is because you can still have all the realism introduced by PBR with the addition of a transparent or translucent effect. If you need transparency for something different, such as UI elements or pixel art, there are more efficient alternatives that are explored in the Creating a transparent material recipe in Chapter 3, Surface Shaders and Texture Mapping.
In order to have a transparent standard material, changing the alpha channel of its Albedo color property is not enough. Unless you properly set its Rendering Mode, your material will...