Some people said that 影 is shadow while 陰 means shade and refers to a shadow or shade that sun or light can't reach. I'm a bit confused.
Basically, 影 is a 2-dimensional shape (with contour) created on a surface by an object blocking light (cast on the surface) and 陰 is 3-dimensional space between the object and the shadow where it is dark.
I think it is better to look at examples to get the idea. And of course, you need to consult dictionaries for figurative uses.