Transparency is useful in plots when you need an unobstructed view of multiple components of one plot, or simply want to lighten a single plot component against a white background. The Wolfram Language uses the graphics directive Opacity to apply transparency to graphics objects. Opacity can be used with most visualization functions.
Use Opacity to see the inner parts of a plot:
Opacity can have values between 0 and 1, with 0 corresponding to perfect transparency:
Use Opacity with a color:
Opacity interacts well with other Wolfram Language functions: