Shade is the general dark area that is protected from the sun:
It's so hot out - let's sit in the shade.
We brought an umbrella to the beach so that we could have some shade.
A shadow is the "shape" of an object or person that blocks the light. You can only have "shade" from the sun, but you can have a "shadow" from the sun OR other types of light, such as electric lights or candlelight.
My dog is afraid of his own shadow.
A lunar eclipse occurs when the moon passes through the earth's shadow.
We can also use the word shadows to refer to a dark area in general:
He jumped out from the shadows of the basement and scared me half to death.
Antivirus software helps protect your computer against known viruses, so you may be able to detect and remove the virus before it can do any damage (seeUnderstanding AntiVirus Softwarefor more information). Because attackers are continually writing new viruses, it is important to keep your definitions up to date.