Could someone explain the investing term “priced in”? What does it mean to be priced in or not priced in?

I’ve heard this term being tossed around while doing research on stocks like Google and Apple. My guess is referring to how both stocks price per share isn’t directly correlated with its performance, but rather on buyer demand (position transaction wise) I may be wrong, but please help me to understand such term. Any information regarding this is greatly appreciated. Thanks i’m advance!