Hello, Sheida,
Both shadow and shade can function as a noun or as a verb. I will break my answer down into examples of both.
Nouns:
Shadow as a noun is the dark form that is cast when light hits something. For example, when we walk in the sun we cast our shadow.
Shade is a noun as well. Within a shadow we find shade. For example, on a hot day we sit in the shadow of a tree because it provides us with shade.
Verbs:
To shadow something means that you follow it. For example, As she walked she was shadowed by an annoying fly.
To shadow can also mean "to cast a shadow" or "to have a shadow cast upon". For example, as she stood her body shadowed the space.
To shade means to darken or to protect from something. For example, he shaded the blue crayon with black to make it darker.(meaning is to darken) Second example, I shaded her eyes from the harsh sun. (meaning is to protect)
I hope you find this answer helpful! Best of luck in your studies!
-Charlie